... if I didn't buy one with the cel that was 
actually created and used by the studio in the 
making of the anime. 

But then somewhere in the description I say "I 
made this background myself on my computer from a 
frame capture."  This is a nice way to display 
cels, and sometimes the only way if the 
arrangement of images relies on props or 
furniture in a missing background.  

But calling a home-made background "matching," 
even with appropriate and honest qualifications, 
could be misleading.