The Nationalmuseum in Stockholm, Sweden’s premier art collection, has released over 3000 images of its works in Wikimedia Commons. It joins other institutions which have announced their own open access policies in recent years, including another major Scandinavian collection, the Statens Museum for Kunst in Copenhagen, and the Walters Art Museum in Baltimore, which likewise chose to release its images through Wikimedia Commons.
You can access the Nationalmuseum’s images here, and read more about the collection here.