A Half Life 2 mod named plan of attack has released their art and sourcecode assets to the public, The art conent contains models and textures (source files). So these can incorporated into your maps!

The download is rather big because of the maps in source engine format but its well worth the download for the textures and props. Go to their website for details:
http://www.planofattackgame.com/news.php

The Plan of Attack Source Code is released under the Creative Commons license. This means anyone is able to copy and distribute modifications of this work, as long as they are non-commercial in nature and you credit the Plan of Attack Team.

Hmm this does not work together with the GPL license used by Nexuiz (for everything, engine AND content)..

But thanks for the tip.

esteel wrote:Hmm this does not work together with the GPL license used by Nexuiz (for everything, engine AND content)..

But they allow to use and modify these models/textures/sounds/etc. for any non-commercial purpose, so it's still a great source for third-party maps & mods.