Pumpkin in a lace stocking. I've planted a bunch of mini white pumpkins. White lace stockings on them might be a nice outdoorsy Autumn touch. Inexpensive and kinda unexpected. These might be cute on the outside tables under the arbor too.
Another mason jar idea! Wash and dry jars and layer the bottom with the greenery of your choice, and then add a handful or two of cranberries. Pour water into the jar, causing the cranberries to float to the top. Insert a floating candle.