Many people keep old photographs in places that seem strange to the average person. In closets, pantries, places like that. My own grandmother kept old photos of friends and neighbours in her linen closet.
Either way, some of these photos get left behind from time to time. Owners of homes die, people move on, and the photos stay there. Some photos are of times, places, things that matter. Other photos are random images of times that were good. Some are of times that were truly horrible.
But at least one of the pictures is, without fail, a dead person. My grandmother had a picture of herself, on the bed she died in, looking aged beyond belief. In my own home, I found a picture of the previous owner with a knife in his hand. The real estate agent who sold the place to me told me that the man who owned the house was killed by his wife.
Every house has pictures like this. Just hope you don't stumble across your own.