In this tutorial we will help you change quickly your desktop background image from the right-click menu (context menu) under Ubuntu 11.10 Oneiric Ocelot. We are going to use the bash script created by gracca from this link.
Open the terminal and install this script with these commands:
mv "Set As Background" ~/.gnome2/nautilus-scripts
chmod +x ~/.gnome2/nautilus-scripts/"Set As Background"
The script is now ready for use. Right-click on any image and select Scripts > Set As Background:
Select an option from the suggested list and click OK:
Your desktop wallpaper will now be changed to the selected image.
[Note]: This script depends on GNOME 3.x to work.