The people over at Batman on Film picked up this from a “reliable source”:
* The Joker will have gray skin with scarring.
* The Joker's costume will be raggedy (This may confirm the info BOF got a long while ago saying that his costume will look as if it was something he put together one piece at a time).
* He's going to look damn scary, not clownish.
The same source later updated the site saying this isn’t a description of the final design, but is “indicative of where they’re going.”
Heath Ledger was cast as the Joker a few months ago.
An image of the character should surface in the next few weeks.