I generally try to reproduce the cels as
faithfully as I can for my gallery (I'm sure we've
all complained about color and brightness woes on
this issue before).  I've never had too much
patience to play with the dust removal tools so
this hasn't been an issue.  However, occasionally
I can't get enough of the cel scanned or it's not
worth it to me.  In that case, I note that the
image is cropped and about how much has been. 
Other than trying to get the colors accurate when
I scan (and adding the watermark), I don't really
do touching up.

I think touched up scans should be noted.  If you
explain the situation fully I think most people
will understand that there's nothing wrong with
the cel, it might just be a little off because of
trying to remove scanner dust (and hey, I love
descriptions).  Really in your case, it doesn't
seem so much like an enhancement as just trying to
get it to look right, but the full story shouldn't
ever hurt. :)  

I know that if I made an offer/reserved money
for/paid for a cel that was very deviated from a
scan I'd be sorely disappointed and a bit miffed.
   I've seen over the years that even with
explaining a background has been added and isn't
matching, things tend to go higher, and the same
would be true for touched up scans.  I think it's
up to the owner to try to provide an accurate a
description as possible if they're going to part
with it.  There's nothing that can be done to
account for the initial reaction to the image, but
at least being clear and honest should give anyone
offering as fair an idea as they can get.

Keys