You mean in the gallery or the cel book? For my 
gallery I like to organize them by whatever way 
looks visually balanced and/or appealing.

In my cel book (yes.. one lonesome cel book 
^^;;), I had once organized it by series, but 
that got messed up quick. So now, if theres an 
empty space, I fill it. I remember when I started 
collecting, that I didn't want to have more than 
1 books worth of cels. So far .. .so good ^^;

~Tara