Looks pretty good.
A while back I was thinking about a game with that kind of overhead view (with rooms and hallways and such). One possible way of making the levels a little more interesting in that kind of game could be to limit the player's vision. A couple games that do this are BOFH (PC and C64 http://www.student.oulu.fi/~loorni/) and Nethack (http://www.nethack.org/).
Of course, it makes the programming a bit more complex, and I don't know your game's design so it might not be suitable. Just thought I'd mention it.