Flickr users offer their photos and images under a creative commons license, and when using for non-commercial purposes, you do not have to worry about royalty.
The East Asia Image Collection (EAIC) is an open-access image archive for the history of imperial Japan (1868-1945), its Asian empire (1895-1945) and occupied Japan (1947-52). Images of Taiwan, Japan, China, Korea, Manchuria, and Indonesia are included. Images unique to this collection include the slides and negatives made from snapshots taken during their years of US State Department service in Asia (1932-1952).
Harvard Digital Collection provides free, public access to more than 6 million objects digitized from Harvard Library collections. They range from ancient art to modern manuscripts and audio visual materials.
Manypixels illustration gallery offers royalty-free images and icons. Every week new batch of illustrations comes out. Tools for Digital Scholarship also employ some of its visual creation.
HathiTrust Digital Library is a large-scale collaborative repository of digital content from research libraries including content digitized via Google Books and the Internet Archive digitization initiatives, as well as content digitized locally by libraries.
The National Archives and Records Administration is an independent agency of the United States government charged with the preservation and documentation of government and historical records. It is also tasked with increasing public access to those documents which make up the National Archive.
The Internet Archive is an American digital library with the stated mission of “universal access to all knowledge.” It provides free public access to collections of digitized materials, including websites, software applications/games, music, movies/videos, moving images, and millions of books.