UNC Libraries Catalog
Biographical dictionaries and encyclopedias provide biographical data (such as birth and death dates and lists of works), bibliographies and essays that are authored by experts in the field.
These institutions offer free downloading of images of artworks from their collections which are in the public domain:
Images in ARTstor with the IAP tag can be used for publishing and educational use, without the need to request additional permissions from contributing museums. More info about the IAP program can be found here: http://www.artstor.org/what-is-artstor/w-html/services-publishing.shtml