Another version

Nicely done, the steel ball is very Escher.

My main complaint would probably be the pixelated "drawing". Soften it up with some blur and gray it down so it looks more like pencil.
Speaking of pencils, yours look more like plastic. Getting rid of the ridges at the tips (remember a sharpener leaves it round) and mapping a natural wood grain bump to that area will help the realism a lot.
Adding an environment map for your surfaces to reflect when they're not facing other objects in the scene would also enhance things, I think.