During my teacher training (PGCE, not CELTA), one of my colleagues taught us about digital photography. He split us into 2s or 3s the day before, and asked us to bring in a digital camera - one for each group. The first half of his lesson involved us going round the college taking pictures.
I'm sure you could base a simple past/present perfect [continuous] activity on this sort of exercise - 'What have you been doing?' 'Have you taken a picture of the library?' 'Where were you when you took this one?
If there's enough time, and you can upload the pictures, they could make a photo-story on PowerPoint or something, with captions and commentary.