What a fun idea! Gourds make beautiful vases. You can use small or large gourds, or even pumpkins. In some cases, you may need to insert a small vase or can inside the gourd or pumpkin in order to hold water for the flowers.
Create a centerpiece arranging different sized "vases," or make several of the same size and repeat them across a mantel or windowsill for a dramatic, festive display.