[Milhouse]

Does the mklocal.py script locally save the artwork that I have chosen, or does it save the default artwork that is scraped after a library scan?

It locally saves the artwork you have chosen, ie. the artwork which is referenced by your media library. mklocal.py will save the full quality artwork so long as it's still available - if the original artwork is remote and no longer available then mklocal.py won't be able to download the full quality artwork and you can optionally have it unset the missing artwork (so that a tool such as Artwork Downloader can subsequently associate new artwork which you can then save locally in full quality), or you can resort to manually exporting the cached version of the artwork that cannot be downloaded.