There are so many lovely ways to arrange book cases. I think that as long as you include things you love and items that tell your story, they will work. Of course a little imagination doesn't hurt either!
One of my favorite ways to display books is via color. Simply arrange your books by jacket color and group them together. You now have instant eye catching bookcases!
Some argue that this makes books hard to find (because they aren't arranged by subject or author), but I guess it all depends on how often you need to pull books off of your shelf.
When we were visiting friends in Brooklyn their bookcases were so pretty I had to take pictures!