Trompe L'Oeil is French for "Optical Illusion".
In the opening scene, the piece of music that can be heard in the background is Claude Debussy's "Reverie" played by a harp.
For the first time, the player piano is playing the show's theme tune, and Maeve shuts it down.
A Krag-Jorgensen rifle is racked behind Lawrence on the train. This sets the time that Westorld emulates as 1886 or later.
At the end of the episode, during the "basement lab" / remote diagnostic facility scene, Ford says "And in that sleep, what dreams may come". Albeit incomplete, it is a quote from Shakespeare's Hamlet - Act 3, Scene 1.