Lawrence, I did a quick pass over your work. You have a good start, yet you can push the contrast further by adjusting the levels on the overall piece. View your painting from afar and make sure that it reads well from a distance. The entire form should read quickly and easily. Remember to keep it simple, stick to a single light source, and remain consistent throughout (the dark side on the weapon is inconsistent with the dark side of the figure). Also, think about form shadow and cast shadow on the figure. For example, the sleeve on the arm should progressively get darker as it turns from the light, and there should be a cast shadows in the appropriate areas when the form blocks the light. Also, remember that the shadow wraps around the form that it rests on. One last thing, is that its ok to loose information in the right areas where shadows meet. It’s a good way to design your value patterns and make the overall read more interesting.

-Nino