Normally the side of the eyes and the mouth have got wrinkles.
I don’t know it this is on purpose, but the’s got this huge wrinkle in his head, which looks odd. It seems that the iron bar on the top of his head is pushing the skin inwards. I don’t think that’s normal, since he’s got a skull too.
His nose seems really weird, it’s like the skin is pulled up.
I dunno, but maybe his mouth needs to go more with the shape of the head. see image.
his head is in an egge shape, the top should be more round.
Nice job, just needs some tweaking