En guise d'introduction, tu peux commencer par décrire rapidement le document (type de doc, personnages, cadre, etc.). Cela sert d'amorce pour tes phrases : tu prends un éléments sur la photo et tu racontes son histoire.
This document is a black and white photograph. On the foreground, we can see an old lady, perhaps Agatha Christie, sitting on a chair and writing on a typewriter. She appears to be focused on what she is writing, maybe because it's very intersting. I suppose she's writing a new whodunnit. It must be thrilling, like all her novels. The photograph may have been taken when she was writing The mysterious Affair at Styles, her first novel. I suppose that she really was enjoying herself : she looks so happy !
Si tu as des questions, n'hésite pas ! =)