I know! Brilliant! Why not a bouquet of leaves? Like flowers they are colorful and seasonal. Unlike most floral centerpieces available in the cooler months, they are FREE! I love free. Free is good. And just like my beloved gourds, they have an extended shelf life. I know! Why had I not thought of this earlier?
Mix different variety of leaves or collect ones in one color. Use a jar instead of a vase or tie the stems with ribbon and place small bouquets of them around the table. But most importantly, I suggest collecting leaves from branches that are within reach. Because, when it comes to putting leaves on your tabletop, you want pristine ones.
Living A la Mode 
How about if you filled the bottom of the jar with acorns? That might look neat.
Love that idea! And the beauty is, you don’t need water to keep the flowers alive so you don’t have to worry about acorns and water turning kind of stinky. If you have only so many acorns, throw a cinnamon stick or two in with the acorns so the bouquet will have a lovely autumn smell.