One of my favorite software for drawing is Art Rage 2. And before you ask, I’ll tell you: no, this drawing is not mine. I’ve put it here only to illustrate this program’s possibilities. The name of the author is David Manuel, with nickname Fashmir (it is written, actually).
Art Rage gives you really big freedom…and not only if you are a gifted painter. :-)
Try it, you won’t regret. Except all, it is not expensive and also there’s a free version.
You can look at the galleries in the forum.
But be careful, you can be easily addicted :-) I warned you…