I ask because the standard message written in the box is not sufficient to understand the why, neither It is clear what I should do to improve that question.
I think KitFox did a fine job of answering your direct question, so I won't bother with that bit.
I think your question could be improved with a paragraph explaining the context of the photo. Perhaps you could talk about what you experienced in the 15 seconds leading up to the taking of the photo.
I was walking through the square, and I came upon a group of people all lying on the ground. Each had a print out on their chest with a political message, and nobody was moving.
What word or phrase could best be used to describe a group of people who lie down in a public place in order to send a political message?
The title could be improved in a similar manner.
Someone please correct me if I'm wrong, but I think it is possible to reopen a question that has been closed, if the question is no longer seen as deficient.
Questions on choosing an ideal word or phrase must include information on how it will be used in order to be answered. For help writing a good word or phrase request, see: About single word requests.
You don't include information on how it will be used. Please also refer to the linked page (About single word requests) for more information.