It is the funny image used as a background on the computer screen, by and large for the desktop of a graphical user interface
As nature and friends gives us a reason to smirk. Anger and antagonism gives us a reason to be cruel.
Similarly, on watching funny wallpapers, it makes us laugh. As proved by research, laughing is as important for a person as air to live happily. There are many moments in our life where we can enjoy and feel the happiness; funny wallpapers help you to keep smiling.
Some of my friends love wallpapers so much that they change it 2-3 times a day. It might be a foolish thing to share but I've noticed wallpapers effect personality. Particularly, for those people who love to write (like me) and are found near the computer almost all the time.