Clients often ask me to help them arrange their bookshelves. I understand that this can be a daunting task, and not everyone reads enough to actually fill them up with books. So if you are not using them in the traditional utilitarian way, then this is a great place to highlight some of your family photos and favorite found objects. With a little down lighting, they can even be the focal point of the room.
Everyone goes about assembling their things in their own way. There is no real guide (or at least not one that I know of) on how to actually do this. For me, it's about balance. For every vertical object on your shelf, you need a horizontal one to counter it (usually above or below it and on the diagonal). You also need stabilizers to finish each run. To translate, usually I like to flank 6-8 books vertically against the side of the bookshelf and then support it with a bookend or a vase. To keep the shelf from feeling too heavy, I usually place something lighter on the other side of the books, like a pair of photographs, a pottery collection, or an interesting box. I will then do the reverse on the shelves above and below the one that I started from (like a zig-zag). Below on my own bookshelves, you will find an antique ladies lap desk, an assortment of nautical tools, a small painting found at a flea market, a gurgling cod, some Chinese pottery, a few reference books, and some of our favorites novels.
Also, bookshelves are a great place to showcase pictures or souvenirs from a trip. One entire shelf can display a grouping of photographs, especially if the frames are similar but in varying sizes, and even more so, if all the photographs are done in black and white. Another shelf can tell a story from a vacation with a few items that you brought home to treasure.
Here are some favorites from my trip to Jordan and Egypt:
And another shelf gets my Balinese wedding couple paired with some antique Chinese buckets:
If you are an avid reader with beautiful hard copy books, then by all means, fill your bookshelves up with books. If you have multiple bookshelves linked together with a center stile, then hang a painting on the stile to break up the line of books. Or, use family photos to act as a bookend at the end of a run. But if you're not reading the books that you put up there, then fill the cases with something more meaningful and something that will strike up conversation when you have company. Anything goes!