Edited for privacy
[name_f]Kamila[/name_f]
[name_f]Alizala[/name_f]
[name_f]Celina[/name_f]
[name_f]Polina[/name_f]
[name_f]Valeska[/name_f]
[name_f]Teodora[/name_f]
[name_f]Rozalia[/name_f]
[name_f]Rafaly[/name_f]
[name_f]Olesia[/name_f]
[name_f]Otylia[/name_f]
[name_f]Melcia[/name_f]
[name_f]Eleonora[/name_f]
Russian
[name_m]Alexei[/name_m], [name_m]Aleksy[/name_m], [name_m]Aleksei[/name_m]
[name_m]Dmitri[/name_m]
[name_m]Feodor[/name_m]
Grigory
[name_m]Ivan[/name_m]
[name_m]Luka[/name_m]
[name_m]Maksim[/name_m], Maksimilian, [name_m]Maxim[/name_m]
[name_m]Stefan[/name_m]
[name_f]Aleksandra[/name_f]
[name_f]Anastasiya[/name_f]
[name_f]Anushka[/name_f]
[name_f]Ekaterina[/name_f]
[name_f]Feodora[/name_f]
[name_f]Isidora[/name_f]
[name_f]Karina[/name_f]
[name_f]Katerina[/name_f]
[name_f]Lidiya[/name_f]
[name_f]Serafina[/name_f]
[name_f]Svetlana[/name_f]
Polish
Augustyn
[name_m]Cezar[/name_m]
[name_m]Dariusz[/name_m]
[name_m]Dawid[/name_m]
[name_m]Eliasz[/name_m]
[name_m]Feliks[/name_m]
[name_m]Jakub[/name_m]
[name_m]Kasper[/name_m]
[name_m]Roman[/name_m]
Tobiasz
[name_f]Angelika[/name_f]
[name_f]Cecylia[/name_f]
[name_f]Dominika[/name_f]
[name_f]Kaja[/name_f]
[name_f]Karolina[/name_f]
[name_f]Klara[/name_f]
[name_f]Luiza[/name_f]
Oliwia
Wiktoria
[name_f]Zofia[/name_f]
I love Polish names a lot! I had to research them a bit for a short story I wrote centered in Warsaw, and my favorite Polish boys’ name is [name_m]Ziven[/name_m]. At least, somewhere I found it on a list of Polish boys’ names. I think I remember its meaning being something like zealous or lively, or something like that. It just struck me as being so cool and yet so approachable. If you go the Polish route, it seems like it’d be easier, in an English-speaking country, to avoid names with "W"s ([name_f]Ewa[/name_f], Wiktoria, Wioletta, [name_f]Walentyna[/name_f], Weronika, etc.), and the extra "J"s and "Z"s (much as I love Jonasz and Gracja, they might cause some extra confusion? Same with [name_f]Sonja[/name_f], [name_m]Eliasz[/name_m], Tadeusz, [name_f]Lilja[/name_f], Lucja, Adelajda (och, much as I adore her!), [name_f]Agnieszka[/name_f], [name_f]Alicja[/name_f], etc. But how hard is [name_f]Alicja[/name_f] to correct? It seems like there’s plenty of Sonjas living in the US, and most Americans catch on; I don’t think [name_f]Lilja[/name_f], Lucja, [name_f]Alicja[/name_f], etc., would be any worse). I think [name_f]Krystyna[/name_f], [name_f]Klementyna[/name_f], and [name_m]Krzysztof[/name_m] are fun, but not usable haha!
I think [name_f]Adela[/name_f], [name_f]Antonina[/name_f], [name_f]Ariadna[/name_f], [name_f]Cecylia[/name_f], [name_m]Bartek[/name_m], [name_m]Marek[/name_m], [name_m]Bogdan[/name_m], [name_m]Damian[/name_m], [name_f]Emilia[/name_f], [name_u]Florian[/name_u], Gracja, [name_m]Jakub[/name_m], [name_f]Janina[/name_f], [name_m]Josef[/name_m], [name_f]Kaja[/name_f], [name_f]Karolina[/name_f], [name_f]Lena[/name_f], [name_f]Leokadia[/name_f], [name_m]Leopold[/name_m], [name_f]Lidia[/name_f], [name_f]Liliana[/name_f], Lucja, [name_f]Magda/name_f, [name_f]Helena[/name_f], [name_f]Maja[/name_f], [name_m]Maksymilian[/name_m], etc. are usable. I met a cute little old Polish lady named Malgorzata at work a year or two ago, and I almost got her name right, and she was seriously impressed, haha. I love the name, but feel like I shouldn’t use it, since I have no tie to Poland other than my short story. 
[name_f]Milena[/name_f], [name_f]Olimpia[/name_f], [name_f]Otylia[/name_f], [name_f]Paulina[/name_f] (I think [name_f]Paulina[/name_f] nn [name_f]Poppy[/name_f] is adorable, but maybe that’s just me!), [name_f]Romana[/name_f], [name_f]Rozalia[/name_f], [name_f]Sabina[/name_f], [name_m]Samuel[/name_m], [name_m]Stefan[/name_m], [name_f]Sybilla[/name_f], [name_f]Tatiana[/name_f], Tobiasz, [name_f]Zofia[/name_f], Zoja, [name_f]Zuzanna[/name_f], etc., are all perfectly usable. In my short story, I used Gracja, [name_f]Sabina[/name_f], [name_m]Ziven[/name_m], [name_f]Cecylia[/name_f], Lilija, [name_m]Adam[/name_m], [name_f]Ariadna[/name_f], Jonasz–in hind sight, probably not the most usable ones, haha, but I still love them a lot!
I’m not as good with Russian names, but I love [name_f]Nadia[/name_f]/[name_f]Nadezhda[/name_f], [name_f]Elena[/name_f]/[name_f]Yelena[/name_f], [name_m]Matvey[/name_m] (discovered this from another [name_u]Berry[/name_u]. I just love saying it! maht-VYAY. I feel like I could actually have a Russian accent lol.), [name_f]Eva[/name_f], [name_f]Oksana[/name_f], [name_f]Yekaterina[/name_f]/[name_f]Ekaterina[/name_f], [name_f]Marina[/name_f], [name_f]Maria[/name_f]/[name_f]Masha[/name_f], [name_m]Mikhail[/name_m]/[name_u]Misha[/name_u], Aleksander/[name_u]Sasha[/name_u], etc.
ETA: For what it’s worth, I think [name_f]Juno[/name_f] and [name_f]Olimpia[/name_f] would make adorable sisters!
I’ll try not to repeat, but I may have missed some.
Polish names that are fairly easy to pronounce:
[name_f]Adela[/name_f]
[name_f]Agata[/name_f]
Aleksander
[name_f]Angelika[/name_f]
[name_m]Casimir[/name_m]
[name_u]Dominik[/name_u]
[name_f]Dorota[/name_f]
[name_f]Edyta[/name_f]
[name_m]Henryk[/name_m]
[name_m]Marek[/name_m]
[name_m]Oskar[/name_m]
[name_f]Salomea[/name_f]
[name_f]Zofia[/name_f]
[name_f]Zuzanna[/name_f]
Russian names (mostly taken from Russian figure skaters, because I’m a dork like that):
[name_f]Adelina[/name_f]
[name_m]Alexei[/name_m]
[name_f]Anastasia[/name_f]
[name_f]Anna[/name_f]
[name_m]Anton[/name_m]
[name_m]Artem[/name_m]
[name_m]Artur[/name_m]
[name_f]Daria[/name_f]
[name_f]Elena[/name_f]
[name_f]Elizaveta[/name_f]
[name_f]Evgenia[/name_f]
[name_u]Ilia[/name_u]
[name_f]Irina[/name_f]
[name_u]Konstantin[/name_u]
Lubov
[name_f]Marina[/name_f]
[name_m]Mikhail[/name_m]
[name_f]Nadia[/name_f]
[name_f]Oksana[/name_f]
[name_m]Oleg[/name_m]
[name_f]Olga[/name_f]
[name_m]Sergei[/name_m]
[name_m]Vadim[/name_m]
[name_m]Valentin[/name_m]
[name_f]Vera[/name_f]
[name_m]Viktor[/name_m]
[name_f]Viktoria[/name_f]
[name_m]Vladimir[/name_m]
[name_f]Zoya[/name_f]
I love [name_f]Anja[/name_f], [name_f]Katia[/name_f], [name_f]Tatiana[/name_f], and [name_m]Nikolai[/name_m] from your list.
Some suggestions that I think work well in English
[name_f]Natalia[/name_f]
[name_f]Oksana[/name_f]
[name_f]Elena[/name_f]
[name_f]Irina[/name_f]
[name_f]Kasia[/name_f]
[name_f]Sonia[/name_f]
[name_u]Sasha[/name_u]
[name_u]Mischa[/name_u]
[name_m]Dimitri[/name_m]
[name_m]Maxim[/name_m]/[name_m]Maksim[/name_m]
[name_m]Stefan[/name_m]
[name_m]Alexei[/name_m]
I study Russian, so I will suggest Russian names.
[name_f]Anna[/name_f]
[name_f]Vera[/name_f]
[name_f]Galina[/name_f]
[name_f]Marina[/name_f]
[name_f]Natalia[/name_f]
[name_f]Lana[/name_f] (short for [name_f]Svetlana[/name_f])
[name_f]Olga[/name_f]
[name_f]Victoria[/name_f]
[name_f]Polina[/name_f]
[name_f]Mila[/name_f] (short for [name_f]Ludmila[/name_f])
[name_f]Milena[/name_f]
[name_f]Anastasia[/name_f]
[name_m]Boris[/name_m]
[name_m]Oleg[/name_m]
[name_m]Stanislav[/name_m]
[name_m]Maxim[/name_m]
[name_m]Stepan[/name_m]
[name_m]Leonid[/name_m]
[name_m]Aleksandr[/name_m]
[name_m]Pavel[/name_m]
Gleb
[name_m]Ivan[/name_m] (ee-VUHN)
[name_m]Victor[/name_m]
[name_m]Vlad[/name_m] (short for [name_m]Vladimir[/name_m]/[name_m]Vladislav[/name_m])
[name_m]Luka[/name_m]
I really love [name_f]Zosia[/name_f]! It always makes me think of [name_f]Zosia[/name_f] Mamet, the actor from Girls.
I’m sure many of these have been said already, but here are some other suggestions…
[name_f]Cecylia[/name_f]
[name_f]Eleonara[/name_f]/[name_f]Eleonora[/name_f]
[name_f]Emilia[/name_f]
[name_f]Izabel[/name_f]
[name_f]Otylia[/name_f]
[name_f]Rozalia[/name_f]
[name_f]Saloma[/name_f]
[name_f]Annika[/name_f]
[name_f]Kira[/name_f]
[name_f]Mila[/name_f]
[name_f]Lilia[/name_f]
I’ve always had problem with Polish diminutives used as full first names, like [name_f]Zosia[/name_f] instead of [name_f]Zofia[/name_f], but I think it’d only be off if you lived in Poland (everybody would assume that [name_f]Zosia[/name_f]'s full name is [name_f]Zofia[/name_f]). Moreover, I wouldn’t use names that contain Polish letters (like ”ukasz you listed, or ”ucja, [name_f]El[/name_f]żbieta etc.) just because they feel incomplete without this additional line or dot.
I’m also looking for names that are Polish (or could pass as Polish), and yet be easily pronounced in English. Someone’s already listed the most obvious differences and I’m sure you’re aware of them, but how much do you care about them? Like the difference between “sz” and “si” that both are pronounced as “sh” in English, making the diminutive of [name_f]Katarzyna[/name_f] - [name_f]Kasia[/name_f] sound like kasza (groats). Does the difference between Polish [name_f]Anna[/name_f] and English [name_f]Anna[/name_f] bother you? (It does bother one Englishman I know - his daughter’s name is [name_f]Emma[/name_f], but Polish kids pronounce two "m"s separately.) You can avoid consonants like “w”, “j” or “c”, but the differences in pronunciation of vowels are impossible to overcome, I guess.
Names that are identical or similar in spelling, but would be pronounced significantly differently:
[name_f]Ada[/name_f]
[name_f]Hanna[/name_f]
[name_f]Julia[/name_f]
Sylwia
[name_f]Klaudia[/name_f]
[name_f]Laura[/name_f]
[name_f]Paulina[/name_f]
[name_f]Diana[/name_f]
[name_f]Maria[/name_f]
[name_f]Eliza[/name_f] (I love this name in Polish, but I really dislike the English pronunciation)
Names with similar pronunciation that I think haven’t been listed before:
[name_f]Amanda[/name_f]
[name_f]Amelia[/name_f]
[name_f]Izabela[/name_f]
[name_f]Daria[/name_f]
[name_f]Teresa[/name_f]
[name_f]Antonina[/name_f]
[name_f]Blanka[/name_f]
[name_f]Helena[/name_f]
[name_f]Linda[/name_f]
[name_f]Monika[/name_f]
[name_f]Aida[/name_f]
[name_f]Daniela[/name_f]
[name_f]Gabriela[/name_f]
[name_f]Sandra[/name_f]
[name_f]Nina[/name_f]
Aniela
[name_f]Anita[/name_f]
Boys’ names altogether:
[name_m]Daniel[/name_m]
[name_m]Nikodem[/name_m]
[name_m]Kamil[/name_m]
[name_m]Filip[/name_m]
[name_m]Bartosz[/name_m]
[name_m]Antoni[/name_m]
[name_m]Tymon[/name_m]
[name_m]Patryk[/name_m]
[name_m]Stefan[/name_m]
[name_u]Dorian[/name_u]
[name_m]Konrad[/name_m]
[name_m]Norbert[/name_m]
[name_m]Robert[/name_m]
(although the “r” sound is problematic)
I really like [name_f]Juno[/name_f] and [name_f]Ada[/name_f] together (either pronounced as ah-dah or ay-də), but probably I’m the only one.