According to Mel Seder:

I want to flash everything from /tmp and put mp3's there to burn to a CD.

Can that cause any problems?

That all depends on what's currently in /tmp, and what's still in use. For example, a lot of sockets used by X11 and the various graphics libraries get set up in /tmp, and removing them while running X might break things.

Feel free to get rid of any large regular files in /tmp, as they're likely not needed after their initial use, and don't sweat the small stuff. Put your mp3's into a subdirectory of /tmp, though, so they're not lost in the mess.