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.
Metallic Leaf Pumpkins: Collect fallen leaves and spray paint them gold; let dry. Paint one pumpkin white and the other gold. When dry, use crafts glue to attach the metallic leaves to the white pumpkin, then arrange the pair together on your porch.