Blizzard has started a promotion on the Diablo III that will allow players to create their own sigil for the Demon Hunter.for
Simply upload a photo (of yourself or anything non-obscene), design a banner, and an exclusive in-game sigil for the player's character will be unlocked.
The site seems to indicate that each class will open individually up through launch. However, it seems that each character will only get a limited amount of time unlocked.
Diablo III will be launched on the 15th May on PC.