So I've got a hobby site I'm working on. I've got items that are tagged and I want to associate those items with photos from Flickr. Even with restrictive searches, I might get results numbering in the thousands.

Requirements:

1. I want to display between 10-20 pictures but I want to randomize the photos each time.
2. I don't want to hit Flickr every time a page request is made.
3. Not every Flickr photo with the same tags as my item will be relevant.

How should I store that number of results and how would I determine which ones are relevant?