Deskscapes does not work on dual monitors for me, where the second monitor is being run in composite mode. The second monitor ends up with a blank screen. This is funny because plain old static wallpaper easily displays on the second monitor. I was using a laptop, running the second monitor out of the HDMI port into an HDMI to composite conversion box, and then out to a composite input on a switch box that outputs to an LCD TV. I have to convert the signal to composite because there are several video sources -- my laptop and two composite video outs on a dual CDG player.
The resolution of the second monitor is supposedly 1024 x 768 according to my windows properties dialog, but maybe the HDMI box converts it into something else.