One of the main problems that become apparent in the permissions world is the fact that many institutions require that anyone who wants to use their image in a book pay for both the image and the permission. But often the institution doesn’t actually have rights to the image if the object is already in the public domain.
Public domain - Digital rights
One thing the British Museum does not allow through their free image service is e-book publishing, but they have adapted to the increasing demand for e-books.
One case that has had a huge effect on how we understand rights to use images in the United States is the Bridgeman Art Library v. Corel Corp. case of 1999.