E. Web-based systems with rich iconographic information, not using Iconclass

In Henri van de Waal's personal archive there was a folder named "Other systems". There he collected information about systems with purposes similar to what he envisaged for Iconclass. Not all of them were systems for the subject access to images.
In a sense this is our page of "other systems". It contains references to websites with subject information about image collections that make use of other vocabularies than Iconclass, or do contain Iconclass internally, but do not offer this information to their end users.
Needless to say this is a very open-ended collection, and we are very grateful for additional information to expand this survey.

Prometheus Bild-archiv is a distributed digital image archive that currently connects 112 databases from institutes, research facilities and museums on a common user interface. Situated at the Institute of Art History of the University of Cologne, prometheus is supported by the non-profit association prometheus e.V. which promotes the ongoing developments of the digital media for science and research.
N.B.: Access is restricted to subscribers.
URL: https://www.prometheus-bildarchiv.de/

The Princeton Index of Medieval Art online database, of which the online holdings complement and partly overlap with the print Index at Princeton University, which is currently being integrated into the database. The collections include images and descriptive data related to the iconography of works of art produced between late Antiquity and the sixteenth century. Although the Index of Medieval Art was formerly known as the Index of Christian Art, it now includes secular subjects as well as a growing number of subjects from medieval Jewish and Islamic culture.
N.B.: Access is restricted to subscribers and Princeton campus.
URL: https://theindex.princeton.edu/
For a comparison of the IMA approach and Iconclass see: The extended hand

The Warburg Institute Iconographic Database, online since 2010. It is an open-access collection of digital images organised according to an iconographic taxonomy similar to the iconographic classification system that Rudolf Wittkower developed for the analogue Photographic Collection in the 1930s. The database contains ca 100,000 images at present -- mainly digitised photos from the Photographic Collection, but also new images from a variety of sources, and even images that are held on external websites, but complement the Warburg's holdings.
URL: https://iconographic.warburg.sas.ac.uk/home

The Thesaurus for Graphic Materials is a tool for indexing visual materials by subject and by genre/format. The thesaurus includes more than 7,000 subject terms and 650 genre/format terms to index types of photographs, prints, design drawings, ephemera, and other pictures. In 2007, the subject and genre/format vocabularies, previously maintained separately, were merged into a single list and migrated to new software, MultiTes. Other minor changes are clarified in the links below. For questions about the thesaurus, contact TGM editors at: tgmed@loc.gov.
URL: https://www.loc.gov/pictures/collection/tgm/
TGM is used by the Library of Congress to give access to its Prints & Photographs Online Catalog (http://www.loc.gov/pictures/)

The Getty Iconography Authority (IA) includes proper names and other information for named events, themes and narratives from religion/mythology, legendary and fictional characters, themes from literature, works of literature and performing arts, and legendary and fictional places. IA is used to record subjects that are depicted or referenced in visual works, but not covered by the other Getty Vocabularies, AAT (generic terms), TGN (geographic names), ULAN (names of people and corporate body), or CONA titles of works.
The IA is linked to the other Getty vocabularies. The IA is linked to other iconography sources, including Library of Congress authorities and Iconclass. The IA has a thesaural structure. It includes equivalence, associative, and hierarchical relationships.
URL: https://www.getty.edu/cona/CONAIconographyHierarchy.aspx?iconid=901000000

The Biblissima portal is a virtual library of libraries: discover the history of various texts and books that were written, translated, illuminated, collected and catalogued from Classical Antiquity through the 18th century.
It has extensive iconographic search functionality. Its controlled vocabulary is based on Mandragore and Fran├žois Garnier's Thesaurus Iconographique.
URL: https://portail.biblissima.fr/