The art was awesome, especially the quasi-3d block dudes (are they pre-rendered?). My only complaints art-wise were the main character and the top-hat wearing statues. I also thought it was pretty neat that the in-game music overlapped the menu music.
My only suggestions are to add co-op multiplayer, sort of like Gauntlet: Dark Legacy. (Ideally local, but I have no idea how you'd figure out the controls for that.) And maybe to make a standalone version of your game, if your engine / tool-set allow it.