That's a perty good attitude
To improve: Check out the Tools, Tuts, and Linkage thread in general discussion. You will find it VERY informative, especially tutorial-wise. Many many techniques there regarding pixel-pushing.
Of course, you should practice the techniques contained within. Lurk a bit in these forums, I think you will find other's works to be inspiring...
Mess around a bit with your paint program, you know. Especially after the tuts and while lurking. It's a somewhat slow (actually, not that slow) progression, but eventually, you would probably produce something you feel really confident about. Post that, recieve crits, remember crits, rinse, wash, repeat.
Crits I can offer on: Color conservation + Contrast. I'm no good at anatomy, so I'd be a hypocrite to berate you on that, haha.
First Piece: Dithering metals *generally* makes the texture dirty and non-metalish. Hair doesn't flow. The text shows rudimentary understanding of AA, but AA can still be learned further (lurk around for that, because AA is quite a different skill to master).
Oh, and the lion pic in the bg, is that hand-pixeled? (We generally frown upon non-hand-pixelage).
Second Piece: Already mentioned Color conservation + Contrast. Will mention again.
