hi hi!
wel... i usually collect from series by chracters 
so i organize by character... except for my 
slayers section, which is separated by season and 
then organized by ep. cause i collect slayers 
focusing on the storyline as well as the 
characters

then within the chracter section, i like to place 
similar cels next to each other in some 
chronological order - like for my chiba mamoru 
cels, i have chibi mamoru then mamoru then tuxedo 
kamen then prince endymion then king endymion... 
now that i think about it, it's kinda odd 
chronological order isn't it?... since they don't 
appear in that order :P... hehe

course, that doesn't hold true for all the 
sections, sometimes it's whatever looks best, 
expecially when i have oversized cels that need 
to fit in somewhere along with the regualr sized 
cels

~ryoendymion