Hello there. I am Jim Bonacci, so here's a relevant review.
I would guess you are going for the style I'm using in Happy Wheels. If that's the case, then what I write following will be a critique on how your drawing matches up with my idea of that style. I think you are off to a good start.
In general I try to keep things simplistic to keep the game rendering quickly. I usually have around 3 shades max for a particular color, which you've picked up on. I like the clothing colors. The skin colors could be a little more contrasty and less pale. A little more shading around the eye will make it look more like a full eye and less like a pupil.
You've picked up on the feathering type of drawing on the clothing and overall it's pretty decent. I would say to use less detail, but to carefully choose where your shadows fall. Your lighting seems to be coming from the front of the character, as the darkest colors are on his back. In order to show a more ambient light source, I tend to draw as if the light is coming from all sides of the character. This way, the darkest areas are the innermost parts, and rotating the character during gameplay won't make it look as if the light source is changing dramatically.
Proportionally, the character could use some help. The torso is a bit too long, and the legs should be longer. Currently they are around the same length as the arms. Judging proportion by eye will get better with practice. Make sure you are happy with the proportions and spacing before completely rendering the character.
I like the stance and implied motion of the character.
What are you drawing these with? I use a wacom and draw in flash.
OK THAT'S ALL I GOT... good job.
[not a member of the review request club]