My go at some shelves, I didn't make them just resized to fit the iPhone 4 and added shadows, then added them to a couple of random walls to see how they look, would love to see some screenshots of these in action so I know they look ok (still waiting for my iPhone 4).
Also here are the shelves without the walls, so you can add your own (the backgrounds are transparent even though they look black).
Thanks for posting, I'm going to be busy with all the great combinations.