First off, welcome to the Guild! And after seeing your first map, I can tell this will be the beginning of a beautiful relationship!
I really have no major suggestions for your map--especially if it was just a test piece. Were I to find things, they would be very nitpicky, and mainly center on the realism you seem to attempt to create. For example, the floor and the wall textures are just a little too "regular"--not enough eye interest to strike one as authentic. The walls are also a bit too symetrical (and straight) to feel realistic. Again, not that these things are "wrong" with your map, just suggestions.
As for design, if it is a wizard, would he have a magical commode?
Great first post! I'm already excited about your additional maps.