May I propose that the plugin adopt the standard caption citation format, using what Creative Commons says is the ideal style?
See https://wiki.creativecommons.org/Best_practices_for_attribution#This_is_an_ideal_attribution
This means providing 1) the title linked to the source image page followed by 2) the author’s name linked to their page, and finally 3) the CC license abbreviation linked to its page.
Ideally separators like quotation marks, parentheses, etc. would be definable in the plugin settings, and any language terms like “by” should be translatable strings.
Author/Photographer names in Flickr have always been a problem if you prefer to have a real name used rather than the username which can often be humorous, profane, or too informal. Does Flickr’s API provide access to the user’s real profile name, if one exists? Sometimes this can only be determined by looking at the user’s personal website if they provide a link or by googling them. I often end up doing that so I don’t have to display usernames like “insane_kl0wn” in photo captions where it would be seen as inappropriate.
