Every time I go straight to Flickr, I get lost or overwhelmed. I often have tried to search for photos using the creative commons search function, but it's so easy to "wander off" that you soon find yourself with pictures you can't use.
However, that being said, it is a powerful tool that can be used any number of ways. I admit I loved using the Spell with Flickr to create my name and think my students would get a kick out using that for their projects.