Not a fan of the eyes.
and think the left side of the picture is better than the right.
lacks something with the depth, looks more like a half mask than a skull, probably something to do with it being a portrait and not having a jaw.
Liking the grainy look.
was the concept work based off a servo skull from warhammer40k?
not bad, but the design could have done with a bit of a follow up check, some parts just look a little odd, the plates and eye on the left make it look sad, while the other side looks scared or shocked