Manual:$wgMimeInfoFile

Details
Sets the MIME type info file, which assigns each MIME type to one of several general categories. The available categories are as follows:

A default mime.info file is distributed with MediaWiki.

Examples: $wgMimeInfoFile = "/usr/doc/mime.info"; $wgMimeInfoFile = null;  // use a limited set of built-in defaults only (defined in MimeMagic.php)