Use steklo's skin and put an image you want into the folder marked background. (Documents>Sports Interactive> Football Manager 2012>Skins>Steklo_x2>graphics>background)
You will need to replace one of the images with yours and name it as the relevant number, i.e. if you delete image 3, call you Rangers image 3.
Edit: This could probably apply to most/all skins but as I use Steklo's i know it works.