Cels Forum

In collecting sailor moon cels I have found more & more mismatched backgrounds...and it has lead me to ask some of the following questons:
1)What are all the different terms reguarding backgrounds?(ie there are matching production backgrounds [usually handpainted]), there are lazer and printed  background copies,solid color paper backgrounds)
2) When diplaying your cels in frame or in gallery, should a mismatched background be kept with the cel, even when it is the one that came with the cel?...(this  is pointless when cel is stuck to said background.
(I have even seen mismatched backgrounds that actually belong with a different cel on a different site.)
3) What is the  general ratio of cels used on one background?
Just curious what this cel community thinks about this.