Sketching for Relaxation

Here is something I spent time on after a tiring day at a customer place. While I've done plenty of hand sketching and paintings, this is my first attempt to do the same using the computer (with just the mouse). And, I think I'm liking it.

I used a simple, yet powerful, tool called Paint.NET. This is an unfinished painting, as there is still a lot of work that needs to go in. Nevertheless I thought of sharing this as it's still OK to be viewed just on a computer :)

Would you like to take a shot at trying to guess what this sketch tries to convey?