Manual:$wgCopyrightIcon

Details
Set this to some HTML to override the rights icon with an arbitrary logo. This is the logo in the bottom left of the footer opposite the MediaWiki logo if using the Monobook skin.

For example:

$wgCopyrightIcon has to be changed in LocalSettings.php

Deprecated
This setting is deprecated in 1.17 and $wgFooterIcons['copyright']['copyright'] should be used instead.