If you have not visited the online collection of the British Museum - I
highly recommend it : http://www.thebritishmuseum.ac.uk/
British Museum - See World Cultures - Use Compass to search the collection
(enter culture in search) - for high quality images.
It is a good site for researching art of ancient and/or world cultures.
Marcia recommended the site to me and now I have it on four pages.
Please post your museum recommendations to the list.