I'm writing this less for the people who actually do these jobs, and more for the soon-to-be brides & grooms who are envisioning their big day and not sure what they should request or want. I hope it's helpful!
Today, we're featuring one little thought about flowers and centerpieces...
If I were a florist, I would alternate heights of flower arrangements across the room:
When all of the flower arrangements are low or all of them are high, it looks nice, but somehow the even-ness isn't as pleasing to the eye as mixing up the heights. Fill in some of the space and add another level of elevation. Consider half low and half high, or 1/3 low, 1/3 high and 1/3 something else (vases with water and a floating candle, or lanterns with a candle inside, for example).