Use sand or pebbles. Some jars can be coated with glass paint to match colored bottles. 12 quart size jars are about Suggest different sizes. Small jelly jars are "quilted" creating a faceted glow from candle.
Twig tree sculpture alternative for xmas. Collect driftwood in summer or trimmings in fall, build a tree for Christmas, and use the bits as kindling to keep warm in January. I'd be tempted to leave this tree up all year round.