Out of curiousity, would characters in outfits/designs similar to Cammy (Street Fighter), Lupinus (Chaos Code), Mai (KOF), Beldachi (My WIP game Brawl Masters which won't be part of this jam), and Catheart (Axel City) allowed or forbidden?
The only one that is clearly allowed here is Beldachi because it's your own character, as long as you make new sprites for her. Characters too similar to existing characters from other games are not allowed, unless you get permission from that game's creators.
I don't think it's a problem, you can go for it. Just don't put their buttocks on show every other frame and it should be fine. As long as there isn't too much focus on their backs, I guess there is no real issue.
