In the course of my research on image indexing and retrieval in the context of websites for museums and cultural institutions, I came across a number of databases that may be of interest to those with an interest in the visual arts.
The Getty Vocabularies databases contain structured vocabularies and terminology for art, architecture, decorative arts and other material culture, archival materials, visual surrogates, and bibliographic materials. These vocabularies conform to international standards and provide authoritative information which can be used to enhance access to databases and web sites. The Getty Vocabularies databases are accept contributions of terms and materials!
-The Art and Architecture Thesaurus (AAT) is a structured vocabulary for concepts related to art and architecture
-The Cultural Names Authority (CONA) is a new, developing vocabulary including titles and attributions for art and architecture
-The Getty Thesaurus for Geographic Names (TGN) is a structured vocabulary for names, descriptions and information for places relevant to art and architecture
-The Union List of Artist Names (ULAN) is a a structured vocabulary for names, biographies and information about artists.
Another database of interest is Netherlands-based Iconclass, used worldwide by museums and art institutions, is a subject-specific classification system designed for art and iconography which aids in the description and retrieval of subjects represented in images. It is a hierarchically ordered collection of definitions of objects, people, events and abstract ideas pertaining to image subject matter.