"human centipede made out of multiple female torsos stacked on top of each other with a split jaw, 4 black and red eyes and cracked skin" I feel like you've thought about this one a little too much haha.
On the colouring side, I'm at the point of working with some artists to really nail down how the player characters displayed so Ill keep things like custom tips in mind though! Anything like that, feel free to mention, its something that's easier to add in early than to have to retrofit later on.
"easier to add in early than to have to retrofit later on." on that note maybe you can add nail coloring? I'm trying to think of things that can be colored different colors like scales and fur... maybe different horn types? I do love horns! What else? Oh yeah! I would recommend looking into RahiMew's "Broken Dreams Correctional Center"'s character creator it has a nice few options.3:
Should I try thinking of something else? like maybe you can add the different kinds of vore types as just temporary copied and renamed buttons of the kill button? or how for tail vore access on any tail type you can add 3 different tail mouth types(player can choose between "o" shaped mouth hole opening, (+)shaped mouth hole opening, or a human mouth shaped hole opening?