You mean models not used in game but in the files still ?
Well, there are the race models for the original alpha character creation screen, in the Interface folder.
There is a Dark Portal in WoD which is an updated version of the original Azeroth one, but not version currently on retail (the unreleased was more faithful to the old one, imo) :
http://www.mmo-champion.com/content/404 ... al-Boss-45I have never found it in the files, so I don't know if it's still there. I would really like to convert it to 3.3.5..
There are various "tools" models for scale reference.
The original Alpha LK mammoth is still in the MPQs I think, that's all I remember.