Fiction, non-fiction, it’s up to you, just make it concise, complete, and captivating. The narrative is a companion to the photo, but it’s not necessarily about the photo. Let the two expand eachother – their relation can be implicit or explicit, but please don’t write a newspaper caption. If you’re looking for inspiration, try browsing some of the existing narratives.
Please note, there is a limit – not to your creativity, but to the number of words. Why? Because it keeps the material bite-sized, and (we hope) makes it better too. It’s been suggested that Twitter’s 140 character limit forces people to edit, thus creating a more thought-out piece of text. So we’ve applied the same here – you have 140 words. Less is fine, of course, but any more, and you’ll find the web form won’t submit.