Use Flickr Storm with your students for locating imagery for digital storytelling projects. It locates multiple photos for you that relate to the keyword and annotates with a Creative Commons license, providing the user name you need for attribution. There is a great tutorial on using Flickr Storm at http://www.jakesonline.org/using_flickrstorm.pdf
Database of images from museum in England. Licensed under Creative Commons - must attribute and also leave embedded meta data in file information. Some very nice images!!