This is a very valuable database of over 1 million scanned digital copies of precious historical documents, pictures, photographs, blueprints, etc. They are all very well categorized. Each database record contains usable meta information about each of the 1 million items - date, medium, people, places, subjects, etc.
Click to see the details: http://www.usabledatabases.com/database/million-gb-digital-copies-of-the-prints-photographs-in-library-of-congress/
Images are almost all 1024px in width or height, larger versions are available via URLs in the database. Here are some samples: http://www.usabledatabases.com/database/million-gb-digital-copies-of-the-prints-photographs-in-library-of-congress/attachment/
Database structure and sample records can be found here: http://www.usabledatabases.com/database/million-gb-digital-copies-of-the-prints-photographs-in-library-of-congress/sample/
Some of the materials in this package are still copyrighted. We are only providing the service to compile the data into usable formats. We are not selling nor re-selling the data. Make your own call as to how to use them in your project.