The official_art wiki says "Artwork that is made by the official company/artist of a series."
However I figure out that the tag was meant for art featured in commercial products, and that the case of artists drawing stand-alone web pictures of their own copyrighted series wasn't really expected (some of the older namori's yuru_yuri was even tagged original).
Do we have a precedent for this?
Updated by RumittanceWuzHere111