These are HL2 models that are included in GMod by default. Verifying your installation may help. If not, try disabling all other addons and then restarting the game. If that fixes it, re-enable your addons in small groups until you find the one that caused it.

I verified it. Still doesn't work. Do you think it's CSS?

I wouldn't expect CSS to affect this. Another addon is more likely.

Try opening the console (Shift+Esc) and then entering the following commands, one line at a time:
After each line, it should show the location that the material/texture files are being read from. It should show something similar to this.[i.imgur.com] If the green text contains the name of another game or an addon instead, unmount/disable it and restart the game.

Oh... my... God. Thank you so much!!!!!!! I know it's just some stupid lockers but i really get uncomfortable with things like that. Thanksssss :D

Yo i'm using this whereis command to locate some other missing textures i have with some stuff. What can i do if it says file not found? Where is this texture folder located also? Is it materials?

Yeah, textures (VTFs) and materials (VMTs) should both be located somewhere in the materials folder. If a file can't be found, it could mean one of the following things:
- The content relies on another game or addon you don't have
- The author of an addon forgot to pack something
- The path you entered is wrong

Keep in mind that a model may have multiple materials, and that each material may depend on multiple textures. They also might not always have the same name or directory, so finding the right paths can be tricky sometimes. When in doubt, contact the addon's author.