Correction, he's using BMP, not JPG. If you are trying to get a critique, use neither. I'm not sure about GIF though, I believe it has a 256 color limit, but of course, you're not going to use that much when coloring/shading work like that.
Rudy, not to be rude, but you didn't do much, except make a couple things slightly better (eliminating pillow shading for the shoes/legs), and everything else worse.
Marc, you don't have to exclusively use black as an outline. In fact, it's actually a better practice you don't at all. Where the light source fades away you should outline it with a darker shade. Where the light source starts, use a lighter shade. Also, darker shades in color theory tends to be blueish. Don't be afraid to use a mixture of colors (ie: blueish green or yellow) for shading opposed to using strictly, say, green. This applies to all your colors, they're too straightforward to actually represent detail. Another note is not to pillow shade, like you did with the shoes and legs. You had the head going in the right direction, but you're disregarding your own light source where his hair is blocking.
The bomb he is holding is ok, but it's a bit dark. Lighten it a bit.
I would explain more, or even show you what I am talking about, but I'm lucky enough to get the time to comment.
Hopefully someone can show you how to shade a bit better.
