Thread:Project:Support desk/Reference to image/file in MediaWiki widget

MediaWiki 1.22.0 PHP 5.3.10 MySQL 5.5.41

I'm trying to include an image in MediaWiki widget-code:

 "test.jpg΅ exists in the "img" map of the wiki, but the image does not show up. How can I achieve this?

Same question for a reference to a JavaScript- or CSS-file.