Desktop background switch

#!/bin/bash    
      
# Check whether the external monitor is connected
xrandr | grep VGA | grep " connected "
             
# 0 is returned on success
if [ $? -eq 0 ]; then
  gconftool -t string -s /desktop/gnome/background/picture_filename /path/to/wallpaper.png
else               
  gconftool -t string -s /desktop/gnome/background/picture_filename /path/to/wallpaper_small.png
fi