To me this looks like some poster or painting held behind the window.
Look at the first image, the "total" of the front. You can see that something rectangular shaped is behind that window. You can see the corner of that in the upper half of the window. Compare to the upper halves of the other windows.
Also not the shadows from the womans legs. The sun apparently comes from the upper-right of that image.
Now look at the close-up image. It seems that there is a fold in the "ghost poster". That folding mark matches the angle of the upper border of that "poster". Then notice the shadows cause by the window frame onto that poster. Notice that there are no such shadows in the other windows.
So, that looks to me like someone held a poster or similar up there. The tilt and matching folding-mark give that away, i think.
Greetings,
Chris