If your dong customs week on my server and your still having trouble with some missing textures. Skyboxes, error messages etc. Plz Read and Install the addons for the missing l4d1 textures that havent yet been adressed.

http://l4dandl4d2mappersforum.eamped.com/2010/04/30/l4d1onl4d2-modified-campaigns-all-in-one-v20-vpk-f/

AND MAKE SURE YOU HAVE L4D2 ADD ON SUPPORT
ALOT OF WORK I KNOW.