I really like the idea of the hallway leading to Vader's isolation room. I see him as way more depressed/introverted than the Emperor, so it's almost like a teenager that stays in his depressing room in the basement and broods all day.

Are there any schematics or whatever out there that show where Vader's room is on the ship?

I think another neat idea might be to have the door close really fast behind Piett, like those ones in ANH. He's already creeped out, plus, the door wants to kills him. Haha.