I just don't get the overkill on Joker and Harley. Harley at least has been pretty consistent with being good in designs. Joker is hit/miss. And certainly we don't need another bust of him. Especially not a great one.
My guesses for the three more drops are:
Another Teen Titan so Starfire isn't lonely
Storm
Witchblade (out of left field, I know, but would round out the three Turner ladies)