Oh, that Skullkid
I guess the only reason I didn't like this as much as some other people is because I thought it would be another Skullboy. You know, the one from "Dad 'N Me"? Nonetheless, this is a good picture in its own right. It seems like you went out of your way to create an original character. I really like how you can see the sketches of this character so well. It looks like he might have a cavity in his chest like something Iron Man would need.
The skull is certainly part of his head. It's a bit hard to tell whether the rest of his body is a skeleton too. I'm guessing it probably is part of his body. This could have been better detailed with maybe more of a background, but it's certainly good in its own right. His arms and fingers make him look like he wearing gloves or some robot suit.