Captain Clown's idea is very appealing, and is one of the reasons I'm for the "permawhite" Joker - not so much for tradition's sake, but because it makes a better dramatic tool. To me, it makes Joker more frightening, more mysterious, and a la Captain Clown's scene, it makes for some very good entertainment. If Nolan wanted to pull a gigantic headfake on the audience (like he seems to enjoy doing in his other films), he'd do exactly what's been described here - make the audience think Joker wears makeup, and then BAM, in one shocking scene we realize it's all a mask under a mask under a mask, etc., etc.
But that's irrelevant to this thread, as someone said earlier. This thread is here to argue why the Joker looks different in each of the pics we've seen so far, not if "permawhite" is a better option or not.
Some argue it's merely technical, others think it's more than that. Perhaps Nolan wants Joker's look to evolve throughout the film - i.e., he never looks the same way twice, with slight alterations each time. Or perhaps Nolan actually responded to fan reactions - after the first pic, many people thought it was an effective look, but perhaps too gruesome. Half of his face literally looked like ground hamburger meat. Now Ledger's scars look like they were toned down, and perhaps that was a conscious measure of fan reaction. And perhaps it's all just one big ruse - if we're to believe Miranda, then we can guess that the Joker has something else going on with his look.
In the end, who knows? We're all here to argue our opinion, and none of us are "stupid" for it.