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.
Tell the story of a person who pretends to be someone she’s not. What complications does she encounter?
Who did you want to be when you were young? How is that different from who you are now?
Write a guide with all the places where one can find costumes and accessories in your hometown.