My colleague and I are planning to submit a manuscript to an academic journal.
As per the journal's policy, the publisher retains the copyright for all content. However, the journal is happy to accept an author's prior self-published content if it was published non-commercially under one of the CC licenses.
Prior to acceptance/final publication by the journal, with the goal of retain the author's individual copyright over them (i.e. not squander copyright to the journal's publisher), my colleague would like to self-publish some figures (used in the manuscript) as standalone images under a CC-BY-NC-ND 4.0 license.
What are the suitable avenues/repositories for self-publishing of these figures?