Firstly, If you do not have counter-strike: Source, a lot of textures will appear purple and black because you won't have the textures and therefore will appear as errors.

Team fortress 2 and/or HL2 textures may be required (however this happens very rarely, also HL2 textures are probably already in Gmod files. I haven't downloaded HL2 nor TF2 and I have all textures for all maps with the exception of some trees on SSRP).

Knives and Vapes are available here if needed:

Cs:go Knives SWEPs
Vape SWEP

Last thing is to type !content in in-game chat on the server to get most ZARP Deathrun content that may or may not give you map textures.

If you need specific maps here is the list for all the maps in Deathrun:

Here

Please let us know if all is well!