It could be a wedding, so guests can contribute their photos of the big day, or a public group devoted to picturesof your neighbourhood, your favourite hobby, or even objects (scooters, peeling paint, muscles...).
Stop Huntingdon Animal Cruelty, agroup that acts as a rallying point for extremists, sets up stalls in shopping malls with picturesof mangled animals and petitions to sign calling for an end to research using animals.