Ok, I was just wondering. It looks really nice. I won full pure in the Christmas lottery, but I have no set to match. I made a nice outline for the head a few weeks ago, but I have no clue how to shade white with grey to make it look like that. It's nice to have kind of a reference picture.
Since nobody actually critiqued it, I'll try my best.
Your smooth shading and attention to detail make this head have a pretty good 3d effect. I think the back of it would look better if that point was more rounded, but it still looks nice as a point. The sparing use of the perforated metal highlights was a nice addition, although I feel like the circle on the front creates too much of a focal point, and draws the eye away from the rest of the head. I'd change the circle into triangle or a V shape and see how it looks. I think it would make it look more 3d and less out of place. I noticed that at the bottom at the back of the head, there's a part that looks either erased, or that it's part of a new layer (it goes from grey to white really fast). You should consider blending this. I love how the eyes work. Thin slits, and the blue glow makes them pop well. Nice lines and highlights to make it look like separate pieces of metal. The tattoo on the face looks nice, but I noticed that there's no colour variation on it (it doesn't shade along with the metal, or if it does, I don't notice).
Overall, very, very nice