Yup, they're all stolen.  Many of my own cels are 
posted on this guy's site.  I've also seen many 
other sites which have galleries of stolen images 
as well.  Most of these sites acknowledge that 
they don't own the cels, and are just displaying 
them as "high quality images."  

Another problem is that a lot of people don't 
understand what a cel displayed on the internet 
is.  When I showed my roommate my site he was 
confused at first as to what the cels actually 
were--he thought they were just screenshots from 
the show.  We need to educate these people!  
Point this guy to:

http://www.animanga.com/cels/info/cels.html

Guys who steal cel images like this are the 
reason that I decided to put my site URL on top 
of all my images.  To those who have not--beware 
of the risk that you are taking!

-Graham