Well those colors from the horse are a natural graphic, light and dark. So you pretty much carried the image with just that.
However, if you are interested in further development, you can consider the structure of the elements and paint those in. Lighting and shadowing has a lot to do with creating volume.
Remember those early exercises (even if you didn't ever try them) where you drew a cube and cylinder, and you showed the planes moving in different directions by making one side a different value than another, and shadowing to show the cylinder turning. Same idea. And break down the parts into planes that you can shade to show the contour changes -- like on the bridge of the nose and the forehead would cascade down as it goes laterally. I'm sure you know what I mean.
Right now, it's clear what you are getting at with the picture, so people would understand the image. But that would be an area of development that you could use in other pictures where you need to show volume for it to make any sense. Also, it's an area that can be turned into an art in itself. Photographers use lighting. So do artists.
Last edited by D Akey; 06-30-2008 at 09:18 PM.
"Not a bit is wasted and the best is yet to come. . ." -- remembered from a dream