Hmm. How about researching old photo postcards of a specific place changing over the decades, with current photos of the same place (taken by you). Ditto the above, but with photos from the local paper.
Then there's the huge topic on how cameras and the media (from Niepce's bitumen process to modern CCD sensors) changed over the years, and how those affected the art and science of photography. But that's a huge topic...
It sort of depends on where you live. I've always liked sociological photography, so if you live in a place with interesting people or a certain peculiar type of people, take pictures of them.
About old photography. Something like the first snapshots with kodak box cameras. How can you relate them with actual snapshots as the made with lomo cameras
