Here are a couple of "before" shots for you. The corner desk is in the same place, and the shelves to the right of my computer is now on the other side of the window.
After I put together the frame of the bookcase, I used 3M General Purpose 45 Spray Adhesive and a black and white damask roll of wrapping paper to add the design to the back of the bookcase. Being able to do this at once is easier than putting the design on the back of each individual shelf.
After the adhesive set (with spray adhesive, after a certain amount of time, it becomes permanent), I affixed it to the back of the bookcase with small tack nails. It is easy to remove, and change out the design later.
The photo above is from the second piece of furniture I added the bookcase, the photo below is the bookcase on the corner desk piece. As you can see, as long as you choose a bookcase with the same, or slightly smaller dimension as your bottom piece, the pieces will look seamless.
Here you can see it in the room.