Try here: www.tessmage.com/

The owner used to mod the game and specialized in skins (albeit, without a lot of clothing :) ); if anyone can help, he can. Now, I'm not a modder and I have no pull with this person so, no promises. Also note, he won't let you register unless you are 21 are older and there was a war between two communities in this game some years ago so do not mention Planet Vampire (or the above site if you are a member there - they both hate each other passionately).

There is a way to change character model during gameplay with console commands. Unfortunately I can't find the commands on google.

There were at least a couple of scripts you could download in the past, but neither download link works now. One of them would let you browse character models with the PageUp and PageDown keys, cycling through all four versions of each clan and gender models at any time in the game.

Alright thanks for what info is available. Seems like a lot is "lost" for this game as far as skins,modding, etc. go.

It's just surprising because the game itself is still actively popular, the unofficial patch is pretty current, can't say that for many games at all that were released so long ago.

Swapping to the model of a different clan is easy. Go to the directory /unofficial_Patch/vdata/system and open the file clandoc000.txt with any texteditor.
In your case find "Player_Gangrel" and replace the model paths with those you find under "Player_Tremere".

The reason why only a few materials (textures) and models are visible in the Unofficial_Patch directory is that most models and textures are vanilla and therefore not extracted from the game archives.
If you want to use some of the alternative models/skins you can find on PlanetVampire, Nexus and some other places, just copy in the apropriate subdirectories in /Unofficial_Patch.