For myself I don't have a cel graveyard site
(mainly because I haven't sold a cel yet), but I
often look into those graveyards.

It's very interesting. A look into the past!
I was able to find up to three earlier owners of
one cel...

Further most graveyards don't offer big size
scans, only small thumbnails, so the only better
scan of the cel can be found at the actual owners
gallery.