I hope there can be more music selection. Although we can add misuc by ourself, it's a pity there is only one music from the official.

@bryant1229 Yes, you are right, you can add your own music
Click on you username on the top right
My music
Click on the music note with the + sign

To also clarify what Manue said, mp3 files are the only file type I have been able to get to work. mp4's and .wav files did not work on my end.