I've had to retouch cels because of my scanner 
too. As for lines, I've never gone that far. I 
would think an owner could photoshop a head of 
Dubya next to their Tenchi image if they wanted 
to, it is their cel after all. Now, it should be 
notated or scanned raw if they are selling it 
because that is a whole different situation. That 
would be misleading to the buyers.