One thing i see when i look at this is that i feel there should be some more detail around the eyes. My attention goes straight to the eyes whenever I look at it, the actual model itself is great but i feel that those eyelids are almost incomplete and as it gets closer to the actual eye it needs more detail. Also the eye itself looks quite crisp, but almost not liquidy and soft enough (imho). Thats the only thing i really see that i would fix in this head of gollum.