I lean closer towards what ImperialFighter suggested when it comes to the hallway idea. The image is nice, but I think it comes across as a bit too isolated. It is something that feels better suited for the Emperor rather than Vader IMO. I feel it's important to remember that often less is more. Since this isn't really a technical error in the strictest sense of the world, I feel any change should be as minimal as possible.

So I'm in favor of just deleting the three imperials outside and keeping the background the same (or perhaps a minor adjustment). By doing so it will look as if Piett had to go through two doors to reach Vader's room, thus giving it a little extra privacy without being too far away from the action.