Fill in the gap between two cabinets?

I moved in to a new apartment. There is a door size gap between the living room and foyer/entrance. I put the book shelf facing the living room and a smaller closed shoe cabinet facing the entrance so that the gap cannot be seen. Now, when you enter, you can see partial backside of the bookshelf above the shoe closet. What can I put up there to fill in the gap? The gap is 2.5 by 3 ft.