SwiftKey comes with 3 skins, and the devs have mentioned "maybe" creating more, but that was awhile ago. The app is great because it learns your typing methods and can be set up to the way you type. It can learn from your Gmail, text, and FaceBook on how you type/msg and doesn't intrude on your privacy.
Skins so far can't be found for it, but I also don't think anyone has given it a try to conquer that hurdle. It would be a challenge worthy of a good dev. (my way of trying to bolster someone to attempt, think it will work? Lol)