Simplicity.

As you said, 100% Realism. But although it isn't a picture you have sat perfecting for hours on end, for what it is, its good. I mean, I can only rate it for its purpose. Being a simple, cartoon style picture, with no need for definition in a realistic way.

So the use of simple shading, and simplicity in general applies well. It would be a good prop in any animated film. But you still have the tone, the shading, the shape, and everything else very well done for what it is.

As I stated, for the simple thing it is, I quite like this.

Nice

Made it my background :P