According to Xboxfocus.com there are leaked images of possible box art. As with CoD4 box art, there were several options rumored before one was ultimately chosen. There are a few things that are bit peculiar with these boxes. One, there is a lack of the number 5 anywhere on any of the boxes, but this may be attributed with rumors of Activision wanting the game to be marketed as Call of Duty: World at War as opposed to Call of Duty 5.
Even more leaked information is making it's way to the internet. These are rumored to be screen shots taken from the game.
Pictures from neocrisis.com