Celebrated children's author Susan Cooper is currently using a photograph of an iconic Scottish location for her official Facebook fan page.
Castle Stalker, on the west coast of Scotland, features in two of her books.
The picture of it, by British photographer Gary Eason, was selected from among a huge range available on the internet.
It shows the castle in bright late afternoon light but with a backdrop of very dark clouds. It is a tone-mapped image composed from multiple originals, a technique that is used to handle the very wide range of light inherent in the scene.
Ms Cooper's Boggart books, in which the castle appears, are lighthearted. But she is best known for darker and more atmospheric fantasies based on English and Welsh legend and it was felt that the mood of Eason's photo was "just perfect for her".
"I'm thrilled they bought my image," said the photographer, who is based in High Wycombe in Buckinghamshire.