If you're stumped on how to decorate shelves, using a collection can be an easy way to go. It's always interesting when you can put together a collection, and by grouping them it can make for a simple solution for shelves.
Here's a collection of old cameras that add a cool, unique vibe for decorating these shelves. By adding a few other objects (like books or boxes) to raise a couple up, you can create some variation in height.
And a couple of individual shots.