I just uploaded a couple images from the old VCL page of "Steve Corbett" and tagged them as "artist:steve_corbett" without realizing that he now goes by "Ironbadger". As we already have at least one image with "Ironbadger" as the artist, can we make "artist:steve_corbett" an alias of that tag?

you could just go delete the steve corbett tags and replace them with Ironbadger? and btw you dont need to put artist: in front of the tag every time, you have to do it only once and after that the site will recognize it as artist tag.