I considered series of terrariums but something about the scale seems off. And the shelf is high enough up (the ceilings are about 12 feet) that you can't really appreciate the detail of the enclosures. Did I mention I LOATHE fake plants? The lack of visible detail problem also rules out groupings of photos for me, but I'm thinking inorganic might be the way to go.
The best ideas I've come up with on my own include a collection of cheap, uniform pottery that reads as a unit (those white Ikea vases are inoffensive if not a little boring) or file folder-y storage boxes (again, bleh but storage is always nice). As you can tell, I'm currently phoning it in with the smattering of crap I have up there right now. I am guessing you guys have much better ideas.
Please share your ideas with Meredith in the comments below...thanks!