Step 3: Decorate
If you cover it up, it is more professional and look less like a hack.
You can use any form of paper.
Actual pegboard hooks work well, but i found brass fasteners work nicely for items that lie flat.
They look swell in combination with the decorated background.
You can combine the brass fasteners with bulldog clips to make it easier to take down and put things up.
In an emergency I don't have to worry about folding the wings and taking the bookcase as is.
Another idea is to attach a sheet of decorated pegboard or Masonite to the back or sides of the bookcase. This will allow you far more display space and give the piece a 'finished' non-mobile look to it.