TL;DR: the Met Museum in NYC updated their collection of images searchable here from Creative Commons; the images are now CC0 1.0 Universal, meaning they can be remixed and even used for commercial applications. Wow! This, and hopefully more moves like this, are part of the Met’s revamped Open Access Policy.
As of today, over 375,000 images of artworks from the Metropolitan Museum of Art are available for you to freely download with absolutely no restrictions under copyright law. The institution announced the effort as part of its new Open Access policy, which includes new collaborations with partners from Creative Commons to Wikimedia to Pinterest to help its collection be as easily and widely accessible as possible.
Since 2014, hundreds of thousands of public domain images from the Met’s collection have been available online for free, but downloads were restricted for non-commercial use and scholarly publication. This stems from the Met’s former policies concerning its own photography of historical artworks. Now, these images are all licensed under CC0 1.0 Universal, which means you can copy, remix, and distribute all of these artworks for any use — yes, even for commercial purposes.
So, cat GIFs! 🙂