Flickr.com serves the dual function of allowing people to search for images and to upload their own images onto the platform. Both of these functions are very useful.
The ability to store information on the web itself - cloud computing if you will - allows us to be free from the machine and the dread of misplacing the usb. The images are stored within Flickr itself, reachable from any pc. I personally uploaded my pictures from a road trip through Germany last year and created a photostream to email to friends and family. As a personal organisation tool, this is fantastic. And Flickr lets you tag your images to produce even more semantic links between your images and the images of different users.
Flickr is a database of images and as such it is a great place to look for images of specific things. Logically, if I am looking for specific images or images about specific things, then other people are too. Flickr is a place where people go to look for images. If someone has heard something about your library, they are as likely to look on Flickr for images as they are to Google it. Therefore, Flickr has great marketing potential for the library. Imagine creating a photostream and then pasting that url on the library's Facebook page or tweeting it out to your followers. The possibilities are endless!