Pillow shading is generally frowned upon at this place, Soldat. This piece had some very unique lineart, even though it was a tad too big for my tastes. However, with the basic shading and colors you just gave it, it seems to suffer from simplicity more than anything. I just don't like the character design, and the pillowshading just killed whatever chance it had of looking good. You might want to study light sources a bit more, and set up a focal point from where light is being created as it's sets upon a surface; in this case, the body parts.
You'll notice light doesn't come to the central point of every muscular division, as you've portrayed here. Also, the dithering seems very off in this piece. It's creating the whole pillowshading illusion, and it ain't 'purrty. I think it would be best to try some simple, flat shading techniques for a base, just to show you where shadows are lying and so forth. Hope to see some improvement...
