There is no way to mark cover art as “wrong release” other than to delete it. Unfortunately you can’t even move it to the right release (you have to delete & re-upload). Notes aren’t even displayed everywhere, so you can’t use those. Even if they were, they’re not machine parsable.
Release disambiguation comments and annotations are a good place to put notes on how to identify a release.
Personally, I delete if:
- wrong release
- I’ve uploaded a better (e.g., higher resolution) version of the same thing. (E.g., there was a small picture of the front cover and I’ve scanned and uploaded a big one).
Remember that a bunch of things (e.g., Picard, several music players) expect CAA to be a source of correct images for a particular release.