Thanks for the comments, guys! I'll definitely check out the river tutorial and I think I'm going to redraw all the mountains (on paper, then scan them in and create a brush from them).

nolgroth: Haha, thanks for the critiques and the comments. I appreciate the interest. And nice catch about the mountains.

jbgibson: Thanks! As far as the mountains... perhaps they're all drunk? I think MyPaint is pretty good. I don't like GIMP at all, though. Perhaps that's just because I'm not used to it, though... you said there are other apps, though. Could you name a few?