You can insure your cels, sure. But are you sure 
the common burglar sees a cel as something 
precious and not just as a campy cartoon pic? 

I think unless an artwork can clearly be 
recognized as a valuable treasure by a known 
artist and NOT just some cartoon animator, 
robbers don't waste their time and risk their 
safety stealing framed goods.

My mother works in a rather rich environment. 
Most of her colleagues collect art and all have 
a PC and a Hi-Fi installation. And Brussels is 
the city of burglary. They have ALL (except us, 
WE're smart ppl who have a dog) been robbed - 
and it was always the PC and high tech that was 
stolen, not some decoration.

Frankly - most ppl who're not familiar with 
manga/anime will prpably find cels to be tacky, 
sissy cartoon "art" for girls and violent little 
boys. They won't waste their time on that.