Welcome. :o) Although I don't have any, I think 
there are a lot of people who collect DBZ cels on 
this forum. They just don't show up in the "Show 
Me" threads, but if you follow links to people's 
galleries, they're often there.

The other advice was very good. Another side note 
which often crops up is if you *do* decide to 
frame your cels, take it to a real art gallery, 
rather than your local MJD or Michaels or Hobby 
Lobby or so on. Or, you can do it yourself. The 
thing is, though, that you want to entrust your 
cel to someone who knows how to handle art... and 
while the high-school sophomore working the 
framing counter might know how to handle a glass 
cutter, or cut a beveled mat, they might not know 
how to frame your cel without damaging it. And 
you don't want to do anything to the cel that's 
irreversible. Go for an open-cornered mounting, 
or something like that, and make sure that the 
materials used are acid-free. You'll want a mat, 
to keep your UV-protected glass from directly 
touching your cel, and so on. :o)

And I think I know the answer to why cels should 
have to breathe... I think it has something to do 
with accumulation of residue over time, which is 
damaging to the cel itself... I'd have to check 
my books, though.

Good luck!
-Cres