To whet your appetite and keep your writing fingers limber, take a good look at the photo, or let a prompt settle in your mind. Set a timer for a reasonable amount of time, be that five, fifteen, or thirty minutes. Then start writing.
Reimagine the Blair Witch Project. What would your characters find if they wandered into these woods with recording equipment?
Have you visited a forest or other place from your childhood that looks different than you remembered it? Write about that experience.
Write about the destination closest to you for people who want view fall colors.