There are quite a few creepy and scary wallpaper options for your Linux desktop. I am going to present a few here that are good for fans of urban exploration.
Prypyat town center abandoned after the accident.
Very creepy fog picture.
Creepy looking sewer photos. These are taken by using a long exposure and then using a flashgun to light up the area.
Old abandoned church in Ireland.
Very old sewer tunnel photograph. One of the oldest sewer systems in the world.
Old mental asylum.