I'd been thinking in terms of a private collector 
or Ebay-er. For an actual cel vendor, though, 
they should take the image down as soon as it's 
sold... and should mark it as being held in 
reserve as soon as they can, after someone has 
made a request for it. I wanted to order a cel 
from a vendor the other day-- and it turns out it 
was being held in reserve for someone else. Even 
though the site's been updated a few times since 
that cel went up, there's no nice little notice 
saying the cel has been spoken for.

So I guess-- in my mind-- if an individual keeps 
a cel image in their gallery, it's okay. As long 
as it's not listed as being currently up for 
grabs, I wouldn't worry. If it was marked as a 
has-been or sold, it's even better. But for an 
actual dealer to not mark a cel after it's been 
reserved, or to not take down a cel after it's 
been shipped--- that's just sloppy and a little 
inconsiderate. :o)

-Cres