I have also seen similar centerpieces that use epsom salts instead of sugar. You could also sprinkle a mix of pearls/gems. Sand (or sugar), faux pearls, a 3 candle. An easy DIY wedding centerpiece idea.
Jello in a vase and drop flowers in it. Use half the water that jello recipe calls for for more vibrant color. you could use lots of different colors, use lots of stuff to toss in there and use them as centerpieces for any party!