-Brushes 32768 Compiler error
-Models 256 Loading map in ET (‘cg_RegisterGraphics: to many inline models: xxx’)
Note: func_explosive creates on model for each explosive object
-tagent 16 Max. length of the tagent. (?)
-Script routines 196 In a scriptblock this is the maximum number of trigger / event routines.
-Note: In the entire script file the total number of routines in multiple scriptblocks can be higher.
-Entities 1024 The game has a maximum of 1024 entities. Of these 64 are reserved by the game for players. It
-also creates entities on the fly (panzershots, mortars).

— Unconfirmed —
-Spline points 512 Was mentioned on the SD forum / Possibly in the Level Designer Reference
-Sounds 256 Found in source code
-Remapped shaders
128 A maximum of 128 shaders can be remapped.


Original Source