Books, books and more books! I've always wanted to have a high-ceilinged room with books from floor to ceiling. so high in fact, that you need one of those slidey-ladders to reach the uppermost shelves.
Built-ins for office. Built ins define an entry via BHG. DIY Built-in IKEA Bookshelves: "Built-in bookcases not only add a ton of character and storage, but they really can make a small house feel so much bigger!