[name_m]Hi[/name_m] there.
Here are my favorite to least favorite rankings:
Girls-
Violet-I love [name_f]Violet[/name_f]. It feels sweet & cheerful but kind of quiet. It’s classic & simple & has beautiful floral imagery. Goes great w/Oliver too.
Delia-This is probably the least popular from your list. I like that about it. But also think that it’s really pretty & kind & slightly exotic while being really easy to say & spell. It’s not the first thing that I’d pair w/Oliver, but it works totally fine.
Eloise-I love this w/Oliver too. It has that same old fashioned witty quirky vibe.
Eleanora-I slightly prefer just [name_f]Eleanor[/name_f], but [name_f]Eleanora[/name_f] is a bit more interesting. And the nn [name_f]Nora[/name_f] makes more sense if you’re into that. I love the nn [name_f]Nellie[/name_f]. Either way, [name_f]Eleanora[/name_f] is strong & bold & feminine.
Madeline-I think that this is light & pleasant. I prefer the Mad-uh-line pronunciation, which feels the most obvious to me. Some people say this Mad-uh-lyn though. I’m not a fan of [name_f]Maddie[/name_f]. Are you? It may or may not be unavoidable. I like the nn [name_f]Maisy[/name_f]!
Hazel-I like it. It’s old fashioned & nature-y. It’s a bit done these days though, but not too bad. It just doesn’t excite me that much.
Claire-Perfectly nice, but just feels a bit…not that exciting.
Matilda-I don’t mind this. I like it for the nn [name_f]Millie[/name_f]. I like it in theory, but it just sounds a little heavy to me.
Cordelia-I love [name_f]Delia[/name_f] & I kind of like [name_f]Cornelia[/name_f] too. So, I should like this! But it feels too over dramatic. No idea why. There’s nothing wrong w/it.
Luna-This is the only name from your list that I’m really not on board with. It’s so so so trendy for dogs. I love dogs! I just dislike trendy names.
A few other ideas that you may like:
[name_f]Adelaide[/name_f]
[name_f]Alice[/name_f]
[name_f]Audrey[/name_f]
[name_f]Beatrice[/name_f]
[name_f]Clara[/name_f]
[name_f]Eloisa[/name_f]
[name_f]Flora[/name_f]
[name_f]Greta[/name_f]
[name_f]Hattie[/name_f]
[name_f]Josephine[/name_f]
[name_f]Lucy[/name_f]
[name_f]Magnolia[/name_f]
[name_f]Mabel[/name_f]
[name_f]Phoebe[/name_f]
[name_f]Penelope[/name_f]
[name_f]Rosalie[/name_f]
[name_f]Thea[/name_f]
[name_u]Vivian[/name_u]
Here are my favorite to least favorite boy rankings:
August-This is just a beautiful name. But in a masculine way! I feel like it’s sharp & smart, sort of artsy & really outdoorsy. And it has cute nns of [name_m]Augie[/name_m] & [name_u]Gus[/name_u]. It’s old fashioned but doesn’t feel over done.
Elliott-I love this too. Well known, not terribly popular, kind of witty & smart & lovable. Gives me similar vibes to [name_u]Oliver[/name_u].
Jack-I love this one too. It feels very friendly & chappy if that makes sense. Feels a bit short next to [name_u]Oliver[/name_u], but definitely not a deal breaker.
Arthur-Cute & geeky in a good way! A bit of a tongue twister to say w/Oliver if you’re looking for reasons to narrow down.
Gilbert-I like this name more in theory than I like the actual sound. It’s quirky & old fashioned & unique. And I love all of the nn options; [name_m]Gib[/name_m], [name_m]Gibby[/name_m], [name_m]Gil[/name_m], [name_u]Gilly[/name_u], [name_m]Gilby[/name_m] & [name_u]Bertie[/name_u].
Eli-I don’t dislike this name at all. I hear it a lot, which makes it a little less special. It’s still handsome though. I kind of like [name_u]Elias[/name_u] more w/Oliver.
A few other boy ideas:
[name_u]Amos[/name_u]
[name_u]Bennett[/name_u]
[name_u]Benjamin[/name_u]
[name_m]Barnaby[/name_m]
[name_u]Henry[/name_u]
[name_u]Julian[/name_u]
[name_u]James[/name_u]
[name_m]Louis[/name_m]
[name_u]Milo[/name_u]
[name_m]Peter[/name_m]
[name_m]Simon[/name_m]
[name_m]Theodore[/name_m]
[name_m]Winston[/name_m]
[name_f]Hope[/name_f] this helps. 
