I'd like to get an opinion on a design for an alien race of mine. They're reptilian and have split into one civilization, one villainous and one heroic and the villainous ones suffer from a mutation. There is a trope called the "Good Lips, Evil Jaws" trope, where the mouths of heroic characters have lips, but the mouths of villainous characters have exposed teeth (like crocodiles). My ideas are; both the mutated and the non-mutated to have exposed teeth naturally, the heroic non-mutated ones have lips (like lizards) and the mutated ones have exposed teeth (like a vicious visual indicator and a by-product of the mutation). I was thinking giving them both exposed teeth to play with a "don't judge a book by it's cover" message, but I'd like to gain some more perspective on this. Thoughts?