The U.S. Library of Congress is sharing some of its old photos on Flickr, including photos of royalty. Best of all, the Library says it "knows of no copyright restrictions on the publication, distribution, or re-use of these photos." Now, that's good news!
Here's one of the first photos made available on Flickr (also available on the Library of Congress website). This is Crown Prince Rudolf of Austria, who mysteriously died in 1889, at age 30, in an apparent suicide.
You can find a list of books about Prince Rudolf's mysterious death here, and DVDs here.