I currently have a HTPC, with my TV as PC monitor.

Only thing is, when I want to do something simple like...change playlist or song ..I need to turn on my TV.

Therefore I would like to have my USB Picture Frame as a second LCD monitor. (The Picture Frame is always on, showing picures, and with the click of my mouse, it is a simple monitor.)

It should be possibile, as Compiz already is using Bitmaps...and you can send Bitmaps over USB and a Picture Frame can handle bitmaps.