I think one of these ended up in the book. We still don't have them here in Australia yet (our comic shops aren't allowed to get them through regular comic distribution due to licensing, so we have to go through secondary retailers). But I really dug both of these. I don't think they ultimately worked for what was needed in the book, but I quite like both these things.
I find the idea of things taking over peoples' bodies internally immensely disturbing, and played with that idea in the design on the right, like it's slowly developed beneath a human skin, then shed it through the mouth.