You have two weeks from today to write a piece of any kind about the photo. The rules are that simple-- literal, abstract, short story, poem, prose, etc. All styles are welcome, just use the photo as a starting point. After the new photo is posted, you may not post writing from previous weeks' photos.
Feel free to write multiple pieces if you feel that inspired, although you aren't required to write for every prompt. You won't be removed as an author unless you you ask to be removed.