Yesterday I spent about 3 hours doing this (till 23:00). I didn't think I was capable of painting the guy, but I actually did well - imo :3
Anyway, I first started off using some faint construction lines, created the face with darker lines, then started going over the lines and creating value with shadow and highlights for a more realistic rendering.
I finally put in the background from the movie poster
put in some red color to create some contrast for the lips (which in my opinion make the character look as crazy as he does) and signed it off :3
Hope you like it... here's the link I used as resource: [link]