Sure the seller could/should have packed it
better, but I have had several packages that were
folded in quarters into my mail box and they said
"DO NOT BEND" on them (they were wedding photos
too, which REALLY pizzzzed me off!).  I sure hope
you had insurance on that package.  Or if not,
then maybe the damage is not as bad with the cel
or sketch inside???  You'll be surprised as to how
durable a cel can be!!

As for my reaction, I would probably scream every
single curse word in the English and/or Japanese
language and roll across the floor screaming "Chi!".