A 6" line of movie-based figures that actually LOOK like the actors in costume would be nice: Michael Keaton as Batman ("Returns" suit), Jack Nicholson as The Joker, Michelle Pfeiffer as Catwoman, Danny DeVito as the Penguin, maybe throw in Michael Gough as Alfred (they could even do a companion line with the first two Superman movies).
For that matter, if they ever do clear up the red tape between WB and Fox, some figures based on the TV series would be neat, too, provided they stick with the "bare essentials": Batman, Robin, Batgirl, Joker, Penguin, Riddler (Frank Gorshin) in his jacket, and Catwoman (Julie Newmar or Eartha Kitt, I'm not particular). If they want they could throw in one of the Mr. Freezes (preferably either George Sanders with removable helmet or Eli Wallach) and the Mad Hatter, but keep any of the villains who weren't in the comics OUT of the line.
As for comic-based figures, I'm not particular, as most of the big Batman artists and story lines either have had figures made in their style already or will at some point for sure...although I'd like to see Bats in his "Batman vs. Predator" armor, Ayatollah Joker from "A Death In the Family", a Dodson-styled Harley Quinn and Poison Ivy, and a 16-inch "Kingdom Come" Bat-Knight.