Most collectors don't want, under any 
circumstances, that their cel images be used. 
This is why they watermark their cels, disable 
the right click, ect. I was very surprised (and 
angry) when I saw a cel of mine that I had posted 
on this forum in an image gallery. (which BTW was 
later removed)

Some fanart looks surprising real. I could have 
saved a lot of cash if I simply had a 
reproduction cel created. IMO, customized fanart 
is far more attractive. It allows for more 
creativity on the artists part, is truely one of 
a kind piece for the receiver and is not 
offensive to the owners of the original cel. Plus 
the signature helps discourage resellers from 
passing them off as original.