It looks pretty good from what you have there, but it seems like you did well on every part except for Michael Jackson's head, which should be the -most- important part. I'd like to see you take this further than a sketch because right now you're not doing one of the best songs of all time any justice by leaving it incomplete :O He was still dark during this video so shade him a bit, give his hair more detail, etc.
Also, I think I'd like to see a little more attitude on his face as well. He was totally badass in this video, so give him more oomph and not so much "careless indifference," if you see what I'm saying. Lift one of his arms up, maybe, or just give him more life in general. He can be lively with zombies crowding him.