There are several ways to add something new to your centerpiece, one of my favorites is using fruit. You can add varies kinds for any season or occasion, using a mix of flowers and vases or just fruit itself. It can also help if your on a budget, many times adding in some colorful pieces will save on flower costs.
This is a good example of cutting cost. Use a bowl, its takes up a larger real-estate on your table and you can find ones similar to this at a thrift store. You can fill the bowl with anything, oranges, grapefruits, lemons, limes then go pull some greenery from your garden and fill the spaces.