I have dealt with the British Museum for many projects, and like most large institutions, they are efficient. Their one major boon, however, is that they created a free online non-commercial use service whereby all of the images of historical (i.e. public domain) objects in their collections may be downloaded and used by scholars. This includes print publications of an academic nature with print runs under 4,000 copies. This is a normal standard for university presses, unlike trade books which are often printed in the tens of thousands.
One thing they do not allow through this service is e-book publishing, but they have adapted to the increasing demand for e-books. For a fee, an image can be used for a specified number of copies in print or electronic form or for a specified time period.