Another pinner wrote In the story, the color black and white is represented in many different ways. This picture symbolizes white as knowledge. This can be related to the Night Circus when Celia and Marco finally came to the realization that they were opponents in the challenge and one of them was meant to die.
The windows in the house I grew up in were quite old, so they had shadows like this. I guess it is because glass is slowly melting, resulting in some areas being thicker than others...or did I dream that? (Jeremie Egry's snapshot?)