"He doesn't own the copyright to any of the 
Dragonaball characters, he just owns a cel. That 
doesn't entitle you to any special privileges."

Actually, if you paid for the item and have legal
proof of ownership of that item (a receipt), then
you have full property ownership of that item. 
This is how a museum can sue anyone that takes
pictures of items in their facility and posts them
(without permission) on their website.  A museum
may not own the copyrights or the trademarks to
the items they have out on display.  But, they do
have property rights on them so long as they show
that they have paid the funds to put them there.

Another thing is that if they take your pictures
from your website without your permission, then
they are also in violation of your copyrights
(your scan, your copyright).  

If they don't remove the cel from Ebay, then
contact their website host and their website host
will remove the site.