Dry the oranges in a low oven for about three hours, then string them with bay leaves and cinnamon sticks. It smells good for weeks and goes on the Christmas tree in December.
TV above the fireplace? Keep everything below the bottom edge of the screen. A low garland, small pumpkins, short candles. Nothing tall competes with the screen.
Four inches of shelf. That's all some mantels give you. So go up the wall instead of across: one leaning piece of art, a thin garland and two tall candlesticks.