Depends on the items and how you want to display them. For example, my wardrobe is either on mannequins or in shadow boxes. All of my DOOM items are kept in one area, displayed together, including mannequins and props. All of my COA's are kept in a folder, except for one that was hand written by the director with a sketch drawn at the bottom, which is displayed next to the costume in a frame. If I have multiple items from a movie, I try to at least display them together, but not necessarily in the same frame or shadow box.