Alien

H.R. Giger's original sketch of the Alien pilot room, with the actual set below it. Imagine being the set manager when Ridley Scott hands you that painting and says "Build this. You have three weeks." All in all, I think they did a fantastic job of it. Fun fact: all painting on the sets involving alien elements -- including the entirety of the pilot room set -- was done by Giger himself with a spray gun, making it possibly the largest piece of airbrush art in history. He insisted that only he could paint it so that it conveyed a properly eerie vibe. He was probably right. That was one seriously weird dude.