It's Richard's dog and John's foot and means nothing at all, other than that everyone thought it'd be a funny cover shot.
We're going through the same thing - trying to find a cover shot for a friend's cd, came across a shot they'd taken of (of all things) a dead mouse next to a bicycle on a cobblestone street, and...voi'la..."there's your cover!"
More often than not, that's the way covers are generally chosen...with artists who are either not too full of themselves or who have a decent sense of humor, anyway.
