The battle between good and bad has always been depicted perfectly well in Star Wars. This is the reason why a million people like it and appreciate it tremendously. As much as possible, they would like to get something that is related to Star Wars showcased on their own screen. In this desktop background, you can see two characters holding light sabers that are glowing brightly against the gray and black gradient background of the image. Their flowing capes seem to showcase their struggle that has been happening for a long time. This is surely a theme background fans will be able to relate to.
See also Darth Vader Windows Theme
Star Wars: Episode VII - The Force Awakens Theme