So the incoming clothing and bites+blood system has different layers for types of clothing or bite + blood marks for injuries, right?
It'd be fantastic for character differentiation to see an expansion on it that corresponds with what kind of body type or tattoos the survivor has. So, maybe a character creation table for a couple body tattoos the same way you might customize a shirt (or however it gets chosen,) or sleeve tattoos if they're a really tough gal/guy.
also! If a survivor has the overweight or underweight traits, they could get noticeably softer looking skin, and maybe contour shadows under their tummy or chest to simulate a belly if they're fat, or shadows to look leaner or frailer if they're thin. Chubby survivors wouldn't have the little rib marks n stuff, thin survivors would have them about as prominent as regular. I think this would really emphasize character differentiation with that same neat little level of detail that has always really charmed me and lots of others with the game.