(sorry posted in wrong categorie before)
Interface:
When you implement more game options/config settings;
Make the mouseover/tooltip info delay adjustable.
Scrolling through the individual idols (idols tab) or room avatars is irritating when the delay (for age, status, etc info) is too long for you.
Event:
During a concerts it should display the playlist and, if it's a factor, their buzz/hype influence on the crowd.
Game mechanic:
Clumsy idols could occasionally stumble into a room and interrupt progress (I'm sure I'll hate that idol after a while ;-) )