A little rushed
I think that you could have spent some time looking over this piece and smoothing out bits and pieces, just to make it look slightly moire human. The skull could be smoothed over, as that's how they tend to come out of the human head. I appreciate the colours would be like that if it had been left outside with no sunlight to bleach it, but the texture would be quite smooth, nonetheless.
Try looking at other skulls - one big piece of detail that you missed is the temple - just behind and above the eye socket on the side of the head, there is what can only be described as a dent. Try looking for some research material and you'll see what I mean. Adding this to the piece would certainly add to the detail and realism for me at least.
How big is this skull? That spider web looks incredibly detailed, to be used on a human sized eye socket. Perhaps you can reduce the amount of detail there, perhaps even adding the spider lazily stalking prey in one corner of the web?
I'm not sure what you're trying to convey in the background, but it's certainly different. An interesting colour scheme and something ominous looming from behind the skull...
[Review Request Club]