Trunk or Treat Decorating Ideas. By Apryl Duncan. Brighten up your trunk with a flower garden theme. By setting the scene with flowers, bumble bees, and a large sunshine, you'll have the prettiest trunk in the parking lot. Garden gnomes or other garden accessories make cheerful additions. Dress up as a gardener, bumble bee, or ladybug to Trunk or Treat Theme Ideas for Any Size Vehicle Please note: You are currently browsing img french quarter theme decorations prom themes that is 500x376px in size. This image is listed in garden theme decorations category. Trunk or Treat Theme Ideas for Any Size Vehicle, 500x376 in 63.47 KB.