I've been working for several days (minus the days I was sick last week) on trying to help a professor get permission to include some famous paintings in a scholarly journal. The paintings are all available in ARTstor, but they don't have the rights to the images, or even know who does have the rights. I have to say the customer service person was very helpful in providing what information they did have, which included which book the images were scanned from and by what participating library. That only helps so much.
So 6 of the 8 paintings she needs are available through a stock photography company. I'm still gathering information about the publication to get a price quote, but as the journal she is intending to submit to will soon be moving to an open-source Web format, I'm not expecting this to be an affordable option.
I'm struggling to understand how artwork doesn't exactly apply to the same copyright rules as text. These are all very old paintings, as in about five hundred years. It seems that copyright should have expired, but I don't think that's how it works. I'm contacting publishers and museums and stock photography companies... I hope I can be of some help to the professor, but this is certainly an adventure!