Out of the ones you've posted, I'd have to say 3 and 4 are my favorites, but even those are somewhat busy. I'd try to work the art into and around the buttons, rather than just having an image with buttons placed on top.
Also, do you need 7 buttons on players 3 and 4? From what I've read and seen, there aren't any games that use more than 4 buttons for those two players.