Definitely a good game, one that should be expanded upon.
Wouldn't so much mind additional characters, but I think Lila, the one you've got there, is cute enough on her own that simple variant outfits would probably serve the game better (maybe unlocked via total score instead of needing to pay a currency for them, or just beating certain songs at given ranks). My only gripe with the AI art is the inconsistent line weight between the stages of undress. That's probably where a commissioned artist would have a leg up.
The timing of the beats of the songs can feel a little... off at times, especially when you get strings of several of the same symbol in a row. On songs like 'Hypnodancer' with a lot of variation and constant switch, it seems fine, though. Maybe I just suck at keeping track of multiple things in the same line, I'm not sure.