these are HL2 prints
Let me explain it to you:
Garry's mod is a MOD. By default, it's a modification of the source engine. All versions of the source engine include half life 2's textures, and gmod took the extra step to include the monsters in it too.
Gmod, by default, only comes with basic source engine textures. Those textures are the same ones used in half life 2, all of them. If you're talking about CSS textures, ask him for those.