Data/Script Item_Shape.csv it will tell you the tpack to look for and where it is
then go to that tpack and open it and that will tell you which dds file(s) it uses
EDIT:
Example:#1
1,Item\Armor\Pants\SWD_EQU_PAT_01.mesh,,0,Item\Armor\Pants\SWD_INV_PAT_01.mesh,,,,2,TRUE,,,,0,0.3,0,1,y,90,1,TRUE,0,0,0
Sometimes there is no tpack (as seen above)
but that dosn't mean there is not one
Item\Armor\Pants\SWD_EQU_PAT_01.mesh go to same spot in the texturepack folder and you will see it
Example #2
5570,Item\Scroll\Etc\skillbook_03.mesh,Item\Scroll\Etc\skillbook_05.tpack,0,Item\Scroll\Etc\skillbook_03.mesh,Item\Scroll\Etc\skillbook_05.tpack,Item\Scroll\Etc\skillbook_03.skel,Item\Scroll\Etc \skillbook_03.anim,2,TRUE,,,,0,0.3,0,1,y,90,1,,0,0 ,0
Here it shows the tpacks just go where it is