First, use 8.1 as 8 is the worst Archicad ever. You surely can find a CD somewhere, same protection key works.
Place the backgrounds in the Background folder of the Archicad library and it will be always available.
The image placed on the plan or any other 2D window is saved with the file.
Djordje
ArchiCAD since 4.55 ... 1995
HP Omen