Simply click the image below of the wallpaper you want.
You will be presented with the image and a selection of screen sizes:
either 640*480, 800*600, 1024*768.
Select the image size appropriate to you screen resolution.
The screen resolution on this machine is currently:
Wait for a while as the full size image is loaded into
your browser window. Once it has fully downloaded, click the right mouse
button over the image and select "Set as wallpaper.." from
the pop-up menu.