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.
Why are these children walking across this field? Write two versions: one in which their intentions are good, the other not so much.
Think about a field or meadow you roamed in your youth. Recall the sights, smells, and sounds you experienced.
Write about the animals and plants that call meadows near you home. No meadows in the vicinity? Write about another ecosystem.