If this is already included in this thread then I agree: -

An object/character selection 'Include - Exclude' dialogue box for both lights and shadows.

eg: - Light 1            lights the character and floor but not the backdrop
                                 casts shadows on the character and backdrop but not the floor

         Light 2            Light the character and the backdrop but not the floor
                                 Casts shadows on the floor and character but not the backdrop

Would have liked this in Poser 8, maybe service release 2 :)