I would love to see the Penguin and definitely catwoman as they are believable characters. It was Catwoman that saved Batman Returns in my opinion. The villians I would like to see, and think fit into Nolan's interpretation are:
Catwoman
Penguin
Riddler
Poison Ivy (as long as she is done in a real way, and not having magical powers that control plants)
Ventriloquist and Scarface
I'm sure there are lots more too