Plenty of book shelves with all the fashion, decorating, art and architecture coffee table books you could imagine. It just needs an oversized comfy chair in the nook to read all those books on a rainy day. And a giant window to look out of.
Spiral staircase. Perhaps a bit wider so it can accommodate a small lift to be installed in the middle. No carpet runner, and branches off to each floor. Ideally, the library would be kinda open, with this in the center.