I absolutely love theater mode and how customizable it is, but I have a few suggestions to improve it:
First, it is annoying that you need to double-click to get it to fullscreen, and then press "escape" twice to get back into library view. It would be nice to have a toggle between "theater mode windowed" and "theater mode fullscreen," so that when you launch theater mode it automatically starts in whichever mode you'd like, and you can get back to your library from fullscreen without the intermediate "windowed mode" step.
It would also be nice to say "automatically start theater mode after player has been idle for X seconds/minutes", kind of like the Zune software. This way if someone clicks a playlist or fiddles with a setting, MusicBee could automatically start up the fullscreen mode soon after. Similarly, a series of ticks that go "Return to library after mouse moves X pixels" and "Only return to library on mouse move if theater mode was started automatically" would be nice.
A few more other things:
-Have MusicBee able to ignore any artist pictures too far outside a specified aspect ratio
-Have MusicBee able to ignore any artist pictures below a certain resolution
-Smooth fade from one picture to the next in Gallery view
-Be able to specify some "motion" so that hi-res pictures could slowly pan a little bit from one corner/side to another, or slowly zoom in or out
-Be able to use the "fade" parameter in Gallery view