What is a wallpaper?
A wallpaper is a decorative paper for the walls of a room
or the background image or set of images displayed on a computer screen or TV.
What does wikipedia say about wallpapers?
A wallpaper or background (also known as a desktop wallpaper, desktop background,
desktop picture or desktop image on computers)
is a digital image -photo, drawing etc. - used as a decorative background of a graphical user interface on the screen of a computer,
mobile communications device or other electronic device.
On a computer it is usually for the desktop, while on a mobile phone it is usual