The “cover art” tab doesn’t have a “replace” function which makes me wonder if when uploading a larger version of an existing art (more pixels) I should remove the existing one? Or maybe the intention is to keep all versions?
What I have been doing is to upload the new cover art I scan, putting it to the front of the list, then marking the replaced art for deletion.
If you are going to remove it, make sure that it is exactly the same cover, back, etc. as the one you are uploading and that yours is substantially better. I missed some small differences on a couple albums - fortunately someone caught me and stopped it. Turns out I actually had a new release in the group!
The top voted issue for exactly this improvement exists since May 2012: https://tickets.musicbrainz.org/browse/MBS-4635
@thebradleys: There is just one problem with your workflow: If someone downvote your new uploaded image, we have no image at all at the end… Therefore we really need some way to replace an image.