Are you talking about a theme? Only the upper few inches will show on the browser, However, if you add a toolbar, or an add-on that has it's own bar, you will see more of the theme.

For example, install this;

https://addons.mozilla.org/en-US/firefox/addon/showip-private/ ShowIP (private)

Shows the IP address of the current page in the status bar . . . . . .

That is really pretty: https://addons.mozilla.org/firefox/addon/the-galaxy-of-andromeda/

I'm not sure what you mean by make it the background. The background of a web page, such as the home page, new tab page, etc.?

Unfortunately, like most lightweight themes, the image is only about an inch tall and therefore isn't large enough to fill the whole browser. Perhaps there is a different kind of add-on for the area you want to fill. For example, the "New Tab Tools" extension lets you choose a background image for the new tab page: https://addons.mozilla.org/firefox/addon/new-tab-tools/

To see more of the Persona you can set a min-height to the navigator-toolbox with code in the userChrome.css file or by using the Stylish extension.

Add code to the userChrome.css file below the default @namespace line.

• http://kb.mozillazine.org/userChrome.css

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* only needed once */

#navigator-toolbox { min-height:200px!important; box-shadow:ThreeDShadow 0 -1px inset; }

The customization files userChrome.css (user interface) and userContent.css (websites) are located in the chrome folder in the Firefox profile folder.

• http://kb.mozillazine.org/Editing_configuration