I'm thinking that this would look so awesome in my soon to be finished art studio. Talk about a creative, upcycled storage solution. It really wouldn't matter what kind of ladder either, as long as it was old looking and still in sturdy condition. A metal ladder would look good in a more modern room, whereas a wood would give such a warm feeling.
These are probably most easily found at antique stores or flea markets as opposed to thrift stores. You could mount it so the bottom rail is horizontal with the ground, but it would also be just as interesting to mount it slightly angled. Your books or display items could easily fit into each section securely.