Using pictures to introduce topics is very common now in schools. However I believe children should be taught how to use a camera properly. Then use their photos to develop ideas and learn about different aspects of our world.
Anyway here are a few I took earlier:
Children can discuss differences between their pictures and how the colours have changed. Where is that light coming from?
The beautiful colours in our world.
Patterns and reflection
Even write stories from their own photos, what is this seagull going to do?