just a quick suggestion for those of you still looking for the floral fill, and don't want to use sand (it'd be too messy for my taste, especially since I'm a klutz and tend to get water all over the counter, etc.) or the aquarium stuff isn't to your taste either--can I make a suggestion?
beads!
seed beads come in tons of gorgeous colors, aren't too expensive (if you buy them in larger quantities and don't get the superamazing handmade glass kind for jewelry), have a bunch of different finishes and sizes, and did I mention they come in gorgeous colors?
ex: (all of these are about $8-9 per pound, and you probably wouldn't need much more than that)
Seed Beads, Delica Beads, Fringe Beads, Bugle Beads - Fire Mountain Gems and Beads
the 'Ming Tree' brand at FireMountainGems is the cheapest, just set it to 'sort by price:high to low' to get to the 1lb packages
hths!
meg
ps- if you have a deeper container, you could always put marbles or those flat stones at the bottom to build up the height and then put the beads on top. those stones and marbles are super easy to find in michaels, craft stores, or the aquarium or fake flowers sections.