Most of the information here is for Warzone 3.1 and above.
3D Models
See gallery of 3D Model images
Editing 3D models:
http://www.misfitcode.com/misfitmodel3d/
http://www.blender.org/
http://www.meshmixer.com/index.html
Other links to check:
http://sourceforge.net/apps/trac/wzgraphicmods/wiki/Dev
http://developer.wz2100.net/wiki/Artwork
http://artrev2100.sourceforge.net/forum/index.php
http://www.blender.org/
https://github.com/Warzone2100/WMIT
http://sourceforge.net/projects/wzgraphicmods/files/obj2pie-win/
http://forums.wz2100.net/viewtopic.php?f=5&t=564#p4645
https://sourceforge.net/apps/phpbb/wzgraphicmods/
https://sourceforge.net/apps/phpbb/wzgraphicmods/viewtopic.php?f=3&t=12