We always urge our couples to consider using our vases and lanterns as part of their table decorations and to feel free to take cuttings right off the ranch.
There's nearly always something in flower, beautiful dried grass stems, green grapevine, etc. Commercial cut flowers are very expensive and almost always end up in our compost, so if you can think local and simple you can save yourself more wear-and-tear and considerable cost.
When considering centerpieces, think about how your guests will interact with them: will they be able to see over and around the creations?
Are you using something too tall and tippy? Centerpieces on mirrors are always a questionable idea!
Maybe in your grandparents' day folks used to hang around waiting to take home a centerpiece, but that seems to have gone bye-bye...