been hunting for textures and remembered when i used to make half-life / TFC maps back in the day there were a lot of textures..
so if you want too you can download your favorite .WAD files or if you have half-life installed you can grab it there. or you can find websites with the .wad texture files like this one.. http://www.cstrike-planet.com/wads
next download Wally either from here (faster) www.nugblazers.com/files/wally_155b.exe
then just open wally with the .WAD file and it will show all the textures in the file and you can export them to .jpg or .bmp or whatever.
maybe this help some with finding textures
PS: you can also edit the textures with wally.. as you could probably notice. just fyi
PS2: if i find anymore good websites with the .wad files ill post them here. see below..
PS3: hmm do textures for OZ have to be 256x256? NM. so far they seem to work if not so thats good
PS4: gonna paste any more links to .wad downloads i find here..