Background Object
The background picture might be a landscape, into which your scene will fit. For this you assign a material, with the required texture in its color channel, to the Background object.
These images will be neither reflected by your scene's reflective objects nor lit in any way by the scene. Nor will they change with any change of camera settings. The background image will show through transparent and refractive objects but will not change with altered camera settings. You could compare it to a background layer generated by the Alpha Channel feature, on which the rendered image is then superimposed.
Foreground and background pictures can also be tiled (see Tile).
Foreground and background pictures are scaled to the output format during rendering. Transparent sections of the background are ignored.
Animations and frame sequences can also be used for foreground and background pictures. In the case of a Background object, these sequences will also be displayed in the viewport.