A good display works on many different levels. One simple way to add height to a display while also enhancing the theme is to hang various items from ribbon or fishing line so they dangle right above the display. For a sport-themed display, you could hang tennis racquets or golf clubs. For an outdoor picnic theme, hang some brightly colored plastic cutlery or glassware. Suspend the props from different heights, and experiment with the ribbon or fishing line so the items hang at different angles (you may need to place strong tape or glue at the back of the pieces to get them to hang exactly as you want). Keep the items in their natural state, or for a more contemporary feel, spray paint them all one color.