A few things I noticed were the angles of where he was attacked. He has lines of damaged flesh going along the ear and the side of the face (a frontal attack) but he has dents where he would have been shot from the side (to the right of his left eye). The flesh on the right side of his skull is almost completely off which makes me think of what could have hit him.
If he was attacked by another machine I could see him getting his flesh ripped from the top of his skull to the back, which I would add a robotic hand print or finger tip marks damaging the other side of his face while his head is being held and flesh on skull torn off.
If he was attacked by ammunition I would make small marks(shrapnel damage) on his neck, nose, brow, and mouth area since he has damage below his right eye. Give your model some expression, maybe an angered brow since Terminators have realistic emotions.
Also, I would leave blots of blood and skin on the metallic skull because the damage was not incinerating nor bashing.
Your model is very detailed and modeling an average mans face compared to a perfect catalog model makes it feel realistic, good work.