With a scaled background image, rubberbanding icons on the desktop damages
the background. The residual bits of image are unscaled.
This is easiest to reproduce with centered/scaled images larger than the desktop.
We (Red Hat) should really try to fix this before next release.
I'm not sure if this is the same or different from the bug where occasionally the
background is not set on the desktop window. The symptoms of not setting the
background will usually be that areas with no icons have a solid-color
background, while areas near or underneath icons do get the image background
drawn. It happens eventually if you sit in background-properties and change the
background enough times.
I haven't been able to find the cause of the problem yet.
Only critical fixes for GNOME 1.x at this point. Relevant code is entirely
different in GNOME 2 so the bug won't apply (though others doubtless will!)