MadSage is a player-created skin that is no longer maintained. The creator, Paul Walker had posted a thread in the official forums with a download link to the MadSage skin which is apparently up and running.
Where to Download
Mordkessel.com has hosted a version of the MadSage skin; see here
How to Install
1. Move the skin.zip file to your shadowbane/skins/ folder.
2. Load up Shadowbane.
3. Hit escape to access main menu, go to Settings, Interface Skins, and select "MadSage".