The terms wallpaper and desktop picture refer to an image used as a background on a computer screen, usually on the desktop of a graphical user interface. 'Wallpaper' is the term used in Microsoft Windows, while the Mac OS avoid mixing terms by calling it a 'desktop picture'. Earlier, the term desktop pattern was used to refer to a small pattern, that was repeated to fill a screen.

Images used as computer wallpaper are usually a data file or structure representing a rectangular grid of pixels. They are points of color on a computer monitor, paper, or other display device, with the same size as the display resolution in order to fill the whole background. Users with widescreen monitors have different requirements, although images designed for standard monitors can often be scaled up or cropped to the correct shape without loss of quality.

Wallpapers are available in double-width versions for displaying on multi-monitor computers, where the image appears to fill two monitors. Smaller images can be tiled or repeated to fill large areas and depending on how skilfully the wallpaper is created, the effect can look good. However, if the joint is too obvious, or the image repeats too many times, it would look very repetitive.

Wallpapers are also appearing on color screen mobile phones scaled to a lower resolution. These are often sold at a high price to telephone users. Some phones have a software which allows images to be uploaded from a computer. Mobile telephones with cameras use images from the camera or from an external source, as the wallpaper.

Wallpaper styles are as varied as people. They can be created using photographs, drawings, 3D renders or abstract pattern with complex gradients. It is useful to have plain areas so that icons can be clearly seen atop the wallpaper.Typical categories of wallpapers include cars, models and celebrities, holiday photos, abstract art, movies, pets and scenery. Wallpapers has a positive effect on the spirits of a computer user as he sees it many times a day. Therefore, selection of an image that appeals to an users personal tastes is important.