The images at http://samlinger.natmus.dk/ are in the public domain or under CCBYSA, so it would be a blast if someone could copy them to Wikimedia Commons and add the {{Nationalmuseet-license}} template to them. The site can be scraped, but there is also https://github.com/NationalMuseumofDenmark/CIP-PHP-Client which may be of help.
Regards, Ole
*) The number will rise to approximately 750,000 if my recollection is correct.