That's cool geamon. The only thing I would try is making it so you can see all the flooring. Later add the doors that block the floors if you want. I'm not sure why I think that's a better way to go except that in other top down maps I have done I didn't and had to go back later and draw in the flooring because a doorway needed to be open. It might not really matter in this case but it might be worth thinking about. (I think I'm going at it from a VTT viewpoint).
Looking forward to where you go with it.