I had some of my cels on exhibit as framing 
samples at the art gallery where I was working 
recently, they were hanging on a large wall 
displaying other types of art and how they could 
be framed. Nothing untoward happened to them, but 
then there was always one member of staff seated 
near them and the cels were in the back. Being 
framed, anyone trying to make off with them would 
have had a hard time concealing them ... I had 
the option of using security hangers to make sure 
they never fell off the wall or got bumped and 
crooked, but since they were in a protected area 
I didn't go that route. Also, security hangers 
make it almost impossible for someone to snatch 
and run, as you need a key to unlock them.

However, I DID have several people pointed in my 
direction when asked if the cels were for sale! I 
dont know if my boss was pleased, we were 
supposed to be selling oil paintings, not my 
possessions LOL

I think as long as the cels are in a place that 
clients dont usually wander, or if they are hung 
securely so that its extremely difficult to 
remove them, you might not have anything to worry 
about. Best of luck!