It is similar to a photobomb as the rack totally hijacks the original focus of the picture. As such, the rack(s) in the rackground are also known as photobombs.
A: There were cows in that picture? Sorry, I couldn’t see anything other than that chick in the rackground.
I was so happy to see that my picture got unintentionally photobombed by that hot school teacher in the rackground.
Did you see the photobombs on that girl in the rackground? I would've totally asked her out if he had seen her earlier.