These are pistachio shells! Hot-glue a second row of shells outside the first, keeping them flat and tucking them between the first row. Finally, hot-glue pistachios to the metal around the candle and place it in the center.
As part of my Salvaged:Reimagining the Familiar exhibit, I painted over a thousand pistachio shells using fine color markers. They were displayed on molding that served as shelves, affixed to the wall, lining up the entire gallery.