While you are grabbing GCFscape, grab vtfedit as well. I would ignore TF2’s textures. They do not look good outside of TF2. And as Valar stated, alot of textures related to Ep2 or newer will, more then likely, need the .vmt file altered.
Alot of links I had for custom textures have gone to crap, but I have a few down there. Try to google search for the ones without a download link next to them as Im to lazy to search for them all:
berneyboy - Large texture pack with urban and natural themes
cncr04s - Huge (1800+) texture pack with everything (some of the vmts are messed up and will need repaired and there is more then 1 texture pack of cncr04s)
HourPitores - Medium texture pack of Industrial and Natural textures Download
ARCRUX - Small texture pack with a sci-fi theme by spineroyal
dr Zaius’ FF Pack - Medium pack of team-colored Fortess textures Download
Gambit01 Texture pack - alot of colored stuff that was made for fortress forever Download