There's something about an old photo or a letter long forgotten, an ancient certificate of birth, marriage or death, that evokes emotion and prompts you to write a story to preserve the provenance surrounding that object.
Here's some examples to get started:
Begin with a photo and imagine the circumstances around it - a wedding photo of all the ladies in the garden - who was there and who was not?
Begin with a letter from a soldier to his family and imagine what it was like at the front.
Begin with a marriage certificate and reveal the history of the couple.
Begin with a baptism record and look for clues on the timing of baptism related to the birth date.
Begin with a newspaper article from the past and tell the story about the event.