This is a great idea. you could even paint or dye the shells to go with different occasions. This would make a nice casual fall wedding table center piece.
These are pistachio shells! To make your own flowering set of votive holders, cut a 3-inch circle from a piece of cardboard. Hot-glue pistachio shells around the edge of the cardboard, pointing the shells slightly upward. Hot-glue a second row of shells outside the first, keeping them flat and tucking them between the first row (conceal as much of the cardboard as possible). Hot-glue a third row inside the first row slightly more upright. Finally, hot-glue pistachios to the metal around the candle and place it in the center. We left our pistachios natural, but you could paint or dip in dye if desired.
Source: Better Homes & Gardens