My mom, sister and I designed these centerpieces for my sister's wedding. They are so easy to make yourself.
What you need:
square vase - ours was 8" square
Mirrored tile (Bigger than your vase, I think ours was 12") If you need more than a couple you can get them at home improvement stores such as Lowe's or Home Depot much cheaper than craft stores
9-12 roses depending on size (per vase). You can mix different colors like we did, but you want all the blossoms to be the same size/diameter, or you can do a solid color
2 pounds of clear glass marbles
tealight holders and tea lights - we used 6 per table[/li]
How to assemble:
Take your roses out of the package the day before and place them in a larger container with warm water. This will get the blooms to really open up wide.
Wash the vase and marbles.
Pour your marbles in your square vase
Cut 9 to 12 roses all the same length (we did ours to where just the tops stick out) and stick them in the vase in rows. (3 roses, 3 rows worked for us) Ha! you're done with that part already
Place the vase on mirror in the middle of the table, get some rose petals of various colors and sprinkle them about
Put out your tealights
We also took a rose and put in each napkin. If you wrap the stems of the rose with floral tape and include a coursage pin, then people can wear the rose as a coursage - clever, I know. The guests loved having the coursage pins.
Optionally you can wrap a length of ribbon around the vase and seal it with a fancy sticker or bow. The bride did not want hers that formal, but I thought it was pretty. We also tried to get these clear 2" stickers with rhinestones on them with their new last name initial "B". That was cute as well, but ultimately we decided to just have them plain.
I think its possible to do this with other types of flowers, but you'll want it to have a hearty stem, so that it could stand up by itself. If you want to use say gerberia daisies, you could try to slip each stem into a green straw (or wrap with floral wire) to give it some stiffness. I'd say you want a trial run before the wedding to make sure everything is just how the bride wants it. Enjoy