Art SACO evolved out of Art NACO (see link at right). Art catalogers in Art NACO have been creating name authority records since 1993 but sometimes need to propose new subject headings or revisions to existing ones. There are several relevant categories of entities that are normally established in LC/SAF rather than LC/NAF: buildings, archaeological sites, and art movements.
Funnel projects in NACO and SACO are groups of usually smaller libraries who work together under a coordinator to create name or subject authority records. Most are organized around a topic or are based in a particular geographic region. There are more than a dozen libraries in Art NACO, most affiliated with museums.
You must file an application with SACO (Subject Authority Cooperative Program of the Program for Cooperative Cataloging) in order to participate by yourself. If you have a heading that needs to be established but you have not registered, I would be happy to help you with the proposal. While I will thank you profusely, you'll only get official recognition on the record if you register.
Web resources for SACO proposals:
ARLIS/NA Cataloging Advisory Committee wiki: