You've done too good of a job not to go all out. If you have to, get a parted out body and head on ebay. I want to see scorch marks, shrapnel, and flayed rubber. Otherwise, I don't think you've reached your full potential.
It's looks like it's burned in the movie. I haven't customized a 12" figure before, but I have put battle damage (blast marks) on sci-fi models. If it were me, I would try a little light work with a dremel and black pastel chalk for the scorching.