Yeah, those are Quake2 textures. They're not part of this mod, and, technically, not legal to redistribute. The only thing you can do is get custom-made replacements or get Quake2's resource files. Problem with using Quake2 is that the textures use a different palette than Paintball2, so they look all messed up.
Edit: Or just don't play on servers running Quake2 jump maps.