1)First off, my gallery is NFS, I've never sold a 
cel.

2)As everyone notes, scanners have issues, color 
balance, contrast, etc.

3)It's a gallery so uniform presentation is a 
consideration, think white bakcgrounds rather 
than gray, borders, sizing of images, etc.

4)I have a graphic design degree and photoshop, 
and I'm not afraid to use them. Seriously though, 
I don't subscribe to "fine art" notions of 
collecting. The very fact that cels aren't 
constructed using archival materials would make 
most fine art types cringe. So I have no issues 
making corrections to some artifacts like 
removing those rainbow-esqe spots and removing 
dust clouding.

*)And as everyone notes should a sale occur(not 
that it will) the above do not apply and raw scan 
should be used.