Hmm, I have some Counter-Strike maps on my Team Fortress Classic servers. The decals.wad file doesn't contain a lot of textures from Counter-Strikes decals.wad.
I added all the TFC + CS textures in decals.wad into a new decals.wad. I wanted to force players to re-download this, but I guess it's not possible
I will just do what teame06 said.
"Tell them to delete the file off there computer."
Thanks