See interestingly shaped clouds from all over the world.
A website where anyone can upload photos and videos of interestingly shaped clouds. You can browse and search by forms, resemblance, geography, etc. You can also subscribe to a daily digest.
It might be interesting to see if there are any patterns or similarities in subject matter and style of pictures taken by people of similar age, and what these are.
An app that crawls the social networks and gathers pictures of users that have their age available publicly. The app then creates an ever growing wall of pictures segmented by age groups.
Get ideas or avoid the clichés.
Point the app at what you want to photograph and see many other pictures taken by others already from different angles and in different styles. Flip through them to get ideas.
Show very similar photographs taken in very different cultures across the world.
Let people search for existing photos already on the site and allow them to upload their similar photos if they were taken in a different country or culture.