by paultgg » Sep 2nd, '11, 18:59
Short version: Disabled Gnome services from running at startup via XFCE settings manager.
Looks like the fake wallpaper was being set the some sort of background Gnome service. Since I didn't install any Gnome config tools (because I didn't install Gnome), there was no way for me to change it. Still don't know if it was a user setting, or a system-wide setting. I'm guessing that XFCE installed some sort of Gnome dependency, so there may be a command-line way to fix it, but I haven't found the config file that references the wallpapers yet (they're in /usr/share/somethingorother/mga, or wheverever they are).