This wiki was in read-only mode for many years, but can now be edited again. A lot of information will need to be updated.
GroundMaterial
GroundMaterial is a option for a [Material] that allows you to set the ground texture to any local, or hosted texture.
Code
To utilize GroundMaterial in your map, first it must be defined:
material name GroundMaterial texture <file name (can be local (for example, 'caution.png), or hosted, with an http:// path.)> end  | 
valid parameters for a Material are: <properties> name=name used to define that its a GroundMaterial texture=set the texture (must be .png but you don't need to include the extension for local textures) </properties>