Background image in X Window

By default, the background in X Window is a grey background. Some window managers have their own options to set other backgrounds, and some don't.

A program you can use to set your background is a program that comes with most Linux distributions. It's called XV, and you can specify which background image you want with this line:

xv -quit -root image.gif

This will set the background to be the image.gif file. You can add that line in your .xinitrc file, in your home directory, so it is executed each time you launch X Window.