PICRYL

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Since the advent of the Internet, combined efforts of finest archives, museums, and private individuals made tens of millions of public domain media files available online. GetArchive created PICRYL to make world's public domain media available to anyone, anywhere, anytime, on any device. PICRYL already provides access to 10+ million public domain objects and growing.

This project is a wonderful source for images and documents, I use it for our wiki.