Yeah I just don't know if that's the best example since the nano doesn't run iOS. I suppose this could be legit and once we see the real thing on Apple's website it will look better. But as I said it seems kind of pointless to load the colored phones with special wallpaper when most people swap out with their own wallpaper anyway.
You do know that's a sticker right? Apple doesn't ship their iPhones turned on. It's just a sticker of the home screen with a pink background. Of course it wouldn't look as good as the real deal.
iOS7 itself would just have all the solid colour backgrounds added to the existing background library and the user could choose whatever they want.