One other point I meant to make- as far as 
collecting cels for the art/beauty rather than 
because you like the series, I think it's fine, 
but if a true "fan" comes along, and you sell the 
cel to him/her, it will probably be easy for you 
to find another "pretty cel" than for them to 
locate a cel of their favorite character.  Just a 
thought, I'm not saying it's something anyone HAS 
to do, but it's something to consider.