I'm not entirely sure if this is a meant to be an Easter Egg or an homage of any sort, but it sure looks familiar. The image you see to the right is in Piero's workshop on the second floor.
At first glance it looks a lot like the portals found in... well, Portal. There's even a note on the wall next to it that reads, "With the proper application of energies, I believe I can transform the door frame into a window of sorts... Currently the step leads to a sheer drop, straight down into the courtyard, but in time it will bridge gaps that will boggle the mind."
There is way too much attention to detail in Dishonored. Amazing.