A photofeed can contain:
- all pictures in an online album
- all images tagged with the keyword "sunset"
- an Amazon.com wishlist
- a list of houses for sale
- a list of desktop backgrounds (used by a screensaver)
A photofeed aggregator is a piece of software that accepts subscribable RSS 2.0 syndication feeds and downloads or precaches higher resolution images (rather than thumbnails) for later viewing, such as when offline. There are not a tremendous number of photo aggregators yet. (please add)