Apparently there's a japanese artist that goes by AG, but AshesG used to go by that name too, so most of the art on the site is tagged with AG, but the artist page links to the japanese artist.

I would've made an alias request, but that would just make it so tagging anything with AG changes it to AshesG.

Is there anyway that any pictures with the AG tag can just have it changed to AshesG, if they're his pictures, or would we have to go through every last pic and change it manually?

ag -source:pixiv would probably be the easiest way to pick out images made by Ashes, assuming the Japanese artist posts to pixiv. Then manually retag those.

Pixiv artist's username is actually AG_121z_lll, their website name is AG_121z. It's important to clean out the AG tags to their proper artists, yes, but AG itself shouldn't be directly used for either of them.

...Their Twitter is ag_69 for the record.