Here is the first WM21 Skin Mod. Its Bret Harts latest WWF Attire from 1997 complete with Hart Foundation Jacket.
Install XXIExplorer (Included in the ZIP file), copy DVD.WAD from Xbox to XXIExplorer Install directory and extract bret_hart.k and bret_hart_entrance.k in the same directory.
Open the XXIExplorer and click "Open-->WAD File-->DVD.WAD" and give it some time to load.
In the now appearing file list, go to "characters\bret_hart.k" and press Import same for "characters\bret_hart_entrance.k".
Now copy the WAD File back to your Xbox HDD and play the game.
Theres a bug in this Version, Brets upper Attire is changed back to normal in the replay. This is due to an, to me, unopenable .res File.