(Snake after you give him a hair cut.)

Really new to dithering, but im hooked. Besides it being awesome I've ran into a few problems with this piece. First, I can't figure out how to make the column look rounded with this shading technique. Second, I can't figure out the colors to make the base of the column stick out more. Third, I can't get the snake to really pop out at ya. If anyone can give me a few pointers that would be awesome.
Peace,
MW360