Yo man I've seen that bones tage before, irl, where you from?

Basically man, you're shading in big gradients, with the lightest color in the middle. That's bascially what pillow-shading is. It's fine to start off, but more realsitic 3d objects dont always have perfectly striped transitional colors like that. It's hard to explain how to do it without showing an example so look at this as ref:

I know you dont care about the ball but you can practice the shading like this like what you said.

Look dude this marble has the darkest shade in the center also shaped like a circle. There's mid value along the edges, with one stream of light on one side,and a little bit of reflected light on the other side. Thats how to do it in this case, but it's not just a way of shading, it also depends on the 3d shape of what you're shading, cuz the volumes are diff.

Yeah I'm not going to explain everything, it takes the fun out of guessing. Here are some examples of cool movie posters:
http://www.imdb.com/media/rm2215155712/tt0121765

http://www.imdb.com/media/rm686266880/tt0083658

Dude man his eyes are shaped like upside-down trapezoids man. Make them smaller, make his pupils bigger. More contrast in the colors, gotta fix up the shape of his nose, plus maybe face. The shading is rough man, face is complex as, no doubt.

Here's a small edit man, this dude looks like a cro-magnus idiot:

Also add lips to him too, mouths are not just lines. The top lip is usually darker,and the bottom lighter.

Now that the contrast is increased you can see the dithering more clearly, where is was subtle before. It also makes it look like she has chicken pox now.