In DBC, there should always be (texturename)
In MPQ, there should always be either (texturename)_u.blp OR (texturename)_f.blp and (texturename)_m.blp. So if your texture is saved as SlaveGirlUpperTorso.blp in MPQ, it won't work. You need to add that _u behind name (or _m and _f if you want to have 2 different textures for male and female characters).
About BLiPster settings, simply make sure that Clothing texture is checked for armor textures (except shoulder and head textures).
128x64 is fine for upper part of torso, for lower it should be 128x32. Or 256x128 and 256x64. Just saying, it seems you have this correct.