From WarzoneWiki

Warzone 2100 offers the opportunity to add lots of new things to the game. Mostly people will create maps and mods which are shared as .wz-files.

Maps

There are lots of maps for Warzone 2100 out there. Unfortunately older maps are not compatible with 2.1 and maps that come in .wdg-files need to be converted to .wz-files.

The .wz-file contains at least a .addon.lev-file and a directory 'multiplay'. To be able to use the map it must be placed in the maps-directory ~/.warzone2100/maps. You should be able to select the map for skirmish and multi player games then.

Mods

Mods also come in .wz-files, but which files are contained in the .wz-file is highly dependent on what the mod does. With a mod wide areas of the game can be changed:

• Graphics (Textures)
• Units
• Buildings
• Sounds
• Research Tree
• Research Topics
• Game Play

To activate a mod you have to use Command Line Options.