Template:FileUrlStyle/doc

By using Widget:FileUrlStyle, this template allows local files to be used in CSS, by assigning them to a class. This is an alternative to FileUrl for mass usage, as it avoids bloating the page with the file URL being repeated.

Note that the wiki doesn't count the file as being "used", and thus if there's no page which embeds the file with the normal  syntax, it will end up in Special:UnusedFiles and may get deleted. So make sure to properly use the file somewhere, like the documentation page for the template the file is being used in.

Example
Adding a background image to text inside a link:   Diamond

Diamond