This is the thingy, inside an internal door window at my house. Some kind of traditional Japanese design. Made of wood, they are sandwiched between two sheets of glass in a frame in the upper halves of the doors. The doors are sliding, and in this image they were open and backlit, so the three layers of glass behind the thingy came out as a solid background. It’s B&W (& a silhouette) too, in real life they are a relatively light natural wood grain.