I would take all the black on the texture and level shift it to a dark dark grey. Vary up the mask with some painted light, grime and scratches. Paint some light on the muscles as well, tint parts of them with a color or 2. Paint in shadows where geometry meets (i.e. horns to head & mask to face, etc...) and change the…
Just be carefull where and how many cast shadows you stick in it if you do that. Cast shadows can look wierd if they stay stationary in a spot that is moved a lot in animation. I agree with the mask to face, but don't know about the horn to head. could I possibly see a wire fram of the ankles I am interested how you did…