Recently, some images about the iPhone 5 which from 9To5Mac and Engadget, the two pictures show similar back covers in black and white. Apart from that, both covers feature a mostly aluminum design with a different material at the top as well as the bottom. The secondary material is possibly glass which can offer better reception than aluminum.
On the other hand, this leaked covers seem to confirm a few previously rumors that the next iPhone is a bit taller and thinner than the current iPhone 4S design and feature a smaller dock connector on the bottom.
The cases like to texture the design of the first iPhone with the iPhone 4 or 4S.