JoJo's Bizarre Adventure had many video games containg skins referencing Hirohiko Araki's works and other sources such as anime, OVA, figures ect. Here's a list of costumes and colors that could be used in a next JJBA video game.
Costumes
Switchable cosmetics
In order not to waste slots, some items on characters can be turn off/on and be combined with other outfits, which would consist of...
Colors
It should be noted in future JoJo games we should have an option to change colors on characters and their Stands separately, even if they have multiple Stands.
Alessi Mode
If they ever make Alessi playable ever again that would mean he would be able to turn his opponents into children during a match. If a character isn't listed here then that means they would have a original/generic child transformation.