Snippets/Direct imagelinks to Commons

Description
With this option you can transparently include Wikimedia Commons media files (images) as if they are stored on the local server. Images not found on the local server are automatically loaded from Wikimedia Commons. Actually the external images are cached on your server (load-through). Supports HTTPS.

Via LocalSettings.php
Since MediaWiki 1.16 it might be sufficient just to set the following flag in LocalSettings.php $wgUseInstantCommons = true;

You might need to configure also the following variables when your host is behind a firewall/proxy: $wgHTTPProxy = "myproxy.mycomp.net:8080";