In anticipation of iPhone 5 arriving next week, I'd like to see which backgrounds y'all are going to be using--especially those that are optimized for the iPhone 5!
Interfacelift has a section now for iPhone 5 (1136 x 640) backgrounds. Unfortunately, while they have some quality images, they are also primarily landscape orientation. That said, have a look at:
InterfaceLIFT: iPhone 5 Wallpaper sorted by Date