There is a fair amount of legalese, but it seems that the Brooklyn Museum is releasing images of all works in their collection with a CC-NC license.
As they say, there are some hiccups:
The Brooklyn Museum is currently researching works that are protected under copyright and contacting artists for permission to use their works. If you can provide contact information for the artist or his/her estate, please contact us.
See Rights and Reproductions for information on licensing text or images for reproduction.
While I am disappointed that they didn’t go full on CC-BY, I have to say I am impressed that the fees for the NC use are *really* clearly defined, and really reasonable in comparison to some of the other Museums we have interfaced with.