Adding materials to a gmod workshop file?

Hey guys.

I’m having a bit of an issue where adding textures to a materials folder within my map workshop won’t actually let people see the textures. Am I doing this right? If so, should I be triple-checking to make sure I’m including the correct textures?

Also side question sort-of related: Adding files to the workshop folder I have won’t work sometimes because these files have capital letters. Why is this stopping it from creating a gma?