Balls
Balls to the wall my friend. Great painting. I'm not sure what you intended to convey by photographing the art. (am I missing something from the "bigger picture?") The accenting of his features makes it really intense where as the color seems dull (again, either your intent via photographing/painting or just poor photo skills). Either way The dullness could be "colored" by utilizing starker contrast with a more colorful background against the dully colored character. The overall style reminds me of another painter but I can't say who for I can't recall.
The last thing that bugs me, which I've hinted at, but am almost certain was not of your intent; taking the photo of the painting at such an angle. Doing this turns the focus towards the photo itself.
If the image is for the canvas, take it straight on with diffused light. In other words, place your art work in such a way that light is not being fully shown on it ie away from the windows Or use an electric light source such as a snake-light and place a film such as tissues or paper of a semi-translucent content to "diffuse" the light.
Keep painting!