Ninjus gives good advice, for instance the yellow hair might be better defined with more orange in the shadow. As for the tutorial he posted, take most everything by that person with a grain of salt, and always disregard their last step entirely. They have a way of inserting something outlandishly stylistic into their tutorials that is definitely not helpful in any way to anyone trying to learn the concepts they teach. It's a shame those tuts are so popular.
You should also pay more careful attention to the outlines, the style you're aiming for works well with crisp 1 pixel wide outlines. So anywhere they start to blob together to form jaggies you could trim down.
It looks like these are edits on top of a base, mind posting them?
