You know, I've been pondering the same thing
for the last month or so... I have two cels 
that are both in this cardboard/frame/mat thing,
and the mat/frame is HUGE!  The cels themselves
are oversized to begin with (the larger one is
12 inches tall by 18 inches wide), but the
matting measures 15 inches tall by 22 inches
wide.  

Frankly, I'm clueless on where to store the
darned things.  The cels show through an opening
in the front, and are unprotected there... and
I notice a few dings on them for this very
reason.  Although they were fairly inexpensive, I 
still
don't want to see them destroyed because I 
can't decide how to store them.  :P

I'm about half a decision away from just taking
the cels out and throwing away the matting/frame.
They're nice looking and fairly sturdy, but 
where on earth do you store something that
size?  :P

I'm interested to see what other people have done
with their inconvenient (but nice looking) and
non-protective matting/frames.  My sister and I
would like to display these some day (whenever
we can find wall space :P), and would like them 
to be intact when that day eventually dawns...

Kim ^.^
aka Lady Zatara

(pic of one of the cels is at the bottom)