Cool little guy!
The top of his head reads strangely, I saw it as a blob eating his head or something. I'm not sure if his head is meant to be transparent showing his brain.
I made an edit using that idea though.
Sorry if it defeats your original idea, i just though this would look a bit better.
I used this
skull as a reference for how I made his skull.
Also I'm just noticing that his ares are identical, I think you should make it so it looks like it goes behind his body maybe.
Hope this helps : D