Maybe you could include some kind of avian or reptile to spice things up? I don't know if they'd really work with your art style, but variety is the spice of life (especialy when every single character is a mammal).
Ps. I know this isn't what this thread is for, but I'd like it if some more of the future alternate versions of characters included more hyper stuff. It's oddly hard to find games here which have hyper content, but I don't wanna pressure you to do something you wouldn't like.