If you find a race/sex combination that the image packs don't cover well, I've enjoyed making characters in Honey Select 2 (or you could use similar character generation software/games like the ones Illusion makes) then making unclothed versions. You can also just do a little photo editing to change hair or eye color on pics from the image packs.
I do this one at a time as I find slaves who need pics b/c I'm borderline OCD about matching their descriptions, but before long I might need to collaborate with the guy who put together the All in One PNG [sic] set to post them all for folks to share.