I threw this together in around 5 mins, I'm currently lacking inspiration of what else to add.
Lemme know.

Arthur Moderated Message:

Programs used pls.

:o nice text color Arthur, I used photoshop CC

I would lower the opacity on the inner shadow that is inside the mouth, or maybe just keep the mouth to an outline. I would then take the eyes and remove the bottom squint wrinkle, but the sphere for the eyes is spot on so that doesn't need changed.

Maybe add some blood splatters, scratches, bruises, etc. to give it something on the side.

Good luck, man.

now I really enjoy simple heads, In my opinion simple is better.
To keep the style of this head consistent I suggest adding some sort of short hairstyle like a buzz or something clean looking. But if you are to make this in the cartoon style maybe try messing around with different skin colors.

Or even have a really simple tribal design going vertically around the eye or something.