More details have surfaced with regards to that "6000 zombies" claim that came out of a Dead Rising 2 talk at the Game Developers Conference last week.
Firstly, that 6000 figure has a caveat. It's how many will be rendered in multiplayer. The multiplayer that has yet to be officially announced by Capcom, and which until now we'd only dreamed about. Since it was a slip of the tongue and not an official proclamation, there were no further details.
And secondly, that the game will feature "at least 800 separate clothing textures", to cut down on that "oh, there's seven of the same dead guy on the screen at once" feeling. Like, for example, the seven "flannel & hardhat" guys you can see in the above pic.
GDC 09: Dead Rising 2 Multiplayer Confirmed [IGN]