He has a very truncated chin. Or is it just his beard that makes it look like that...? Not that it looks unrealistic, mind you - he's just not very handsome. Which was probably your intention, so good work.
I used poly painting. Basically, I layered the texturing one pass at a time. First, I establish a base color, then I paint in colors for blood and veins and bone and then I apply the base color again. If that's not enough, I finish off with whatever other little details will get the job done. Watch the vid here by Scott Spencer to get an idea of this process: [link]
If I'm in a rush or I'm requested to do so, I may also use photo textures, which I paint on in place of the base color in the method described above. I hope that helped.