I love [name_u]Jan[/name_u] as a shortened name not sure which longer form
[name_u]Janis[/name_u] (this is my preferred spelling)
[name_f]Janet[/name_f]
[name_f]Janine[/name_f]
[name_u]January[/name_u]
[name_m]Feel[/name_m] free to give suggestions
[name_u]January[/name_u] is my favorite!! I also have an aunt named [name_u]Janis[/name_u] who goes by [name_u]Jan[/name_u], and it suits her well 
Other suggestions:
[name_f]Janette[/name_f]
[name_f]Janetta[/name_f]
[name_f]Jana[/name_f]
[name_f]Janae[/name_f]
[name_f]Jane[/name_f]
[name_f]Junia[/name_f] maybe?
I love [name_u]January[/name_u] 
Other suggestions:
[name_f]Janessa[/name_f]
[name_m]Jansen[/name_m]
[name_f]Jessalyn[/name_f]
[name_f]Jessamine[/name_f]
[name_f]Janelle[/name_f]
[name_f]Janna[/name_f]
[name_f]Joanna[/name_f]
[name_f]Joanne[/name_f]
[name_u]Jaylyn[/name_u]
[name_f]Jasmine[/name_f]
[name_u]Jordan[/name_u]
[name_u]Jaden[/name_u]
[name_f]Julianna[/name_f]
[name_u]Julianne[/name_u]
[name_u]Jameson[/name_u]
Jennilyn
[name_f]Jolene[/name_f]
[name_f]Josephine[/name_f]
[name_u]January[/name_u] is fun and sparky! [name_f]Janet[/name_f] is kind of fun too!
I think [name_f]Janae[/name_f] would be my favourite that isn’t on your list, but I also thought of:
[name_f]Janina[/name_f]
Joanna/Joanne
[name_f]Janelle[/name_f]
Lujayn
[name_u]January[/name_u] was my first thought! [name_f]My[/name_f] other ideas have all already been listed
[name_u]January[/name_u] is my favourite I love the sparkly wintry imagery she provides the overall dark academia vibe feels cool. [name_u]January[/name_u] is very unexpected. This is closely followed by [name_f]Janet[/name_f] she’s a family name for me and feels nostalgic, cosy and inviting.