This is a diagram:
Look at the background carefully...
This background was made in compositing: http://www.filedropper.com/xtruder22
However, I wanted to know whether I could put a better background gradient from a .jpg or .png file? e.g.: http://www.shoutot.com/stockimage/black-gradient-background.jpg http://fc07.deviantart.net/fs71/f/2013/042/c/3/gradient_toshiba_background_by_daproba-d5uo24e.png
Many thanks