This information comes from the GPL Wolfenstein source code. I’m working on documenting the BSP file format, so this is an excerpt from my notes:
BSP file format for Quake 3 / Return to Castle Wolfenstein
Map limits for Wolfenstein:
Models - 1024
Brushes - 32,768
Entities - 2048
Shaders - 1024
Areas - 256
Planes - 65,536
Nodes - 65,536
Brush sides - 65,536
Leafs - 65,536
Leaf faces - 65,536
Leaf brushes - 65,536
Portals - 65,536
Lighting - 4,194,304
Type /shaderlist in the console to see the list of shaders. If there are more than 1024, you will get the shader overflow problem, usually when you fire a machine gun or take a hit. Changing from lightmap to vertex lighting will reduce the shader count.