Hey so I noticed my art on here a while back. I'm actually glad to see some of my stuff picking up here, but I've stopped using Pyanny as an artist name.
I was hoping to change the tag to Byuni, I've tried editing one of them myself but I think I messed up. Not sure how this site works exactly, but if anyone could assist me that would be great.

You changed the one post correctly. You can manually update the rest of the posts under pyanny-yan (just remove the old tag and add the new) , and possibly create an alias request as well (if you still use that name in other places).