the built-in bookcase shelf wall is such a great idea. the shelves are different heights and would normally end into a wall. Keeping the right side open creates a larger room, and force your eye to look at your collectables. How to display your shelves.
a hinged full length mirror from IKEA (Stave mirror - that is x hides jewelry storage -- brilliant idea from The Girl on the Go! I would use a thin sheet of plywood cut to fit behind the mirror so I don't put so many holes in the wall.