[Juan Mortyme]

@MB1968
@Juan Mortyme
Here's what I've found so far in Leia...

1. If you have the online artwork enabled in Universal Artist Scraper, Skin Helper displays the fanart images from the online source (fanart.tv for me) in your database. When I disabled the online artwork, Skin Helper displays the images from the Artist's extrafanart folder.
2. I added a new option to use Artwork Helper to display the fanart images. This will allow you to remove your extrafanart folder if you so desire and place the fanart images in your Artist folder (similar to Movies...fanart.jpg, fanart1.jpg, etc.). However, the extra fanart only displays for Artists...the album and song view displays only the default fanart. I can look at adding additional fanart options just for albums and songs so that their fanart operates independent from Artists.
3. The fanart in the Shelf3D and Shelf3Dv2 thumbnail window in the upper right will display the default fanart, or display images from the extrafanart folder if the path is selected in the Top Menu above SHOW ARTIST/ALBUM ART. Also, the setting SHOW ARTIST/ALBUM ART now enables/disables the extrafanart for that thumbnail window in both views.
4. Having the first image in the extrafanart folder named fanart.jpg or fanart0.jpg doesn't seem to matter...it displays either way.
5. The discography in Music Info is being displayed via Universal Artist Scraper. I have mine set to use Musicbrainz.

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@wags1
Once I get this all figured out in Leia, I will move on to Matrix.

And therein lies the answers:

First, to why @MB1968 is seeing online art and I'm not.

I turn off ALL artwork download options in ALL add-ons including scrapers in an abundance of caution to guarantee  compliance with my strictly enforced "Artwork Protection Act". I never would have suspected an official Kodi scraper of being a rouge sleeper activated anytime other than when adding media to the library or the issuing of a "Reload" command? In fact I'm sure I've seen members of the High Command (aka Kodi Development Team) testify that is the case. 

Second, it also explains why sometimes artist discography is displayed and other times not.

I'm not nearly as diligent guarding metadata because .nfo files trump scraper results unless "Prefer Online" is enabled in Main Settings>Media>Music and/or Artist Slideshow. That and an infiltration of metadata doesn't do anywhere near the damage done when artwork gets contaminated. It happened to me once and it took me a long time to sterilize and rebuild my artwork, hence my seemingly paranoid defensive overkill on the artwork front. Ever since then I've added my Artist Information, Movie Set Artwork and central Actors folders to be included in my routine backup of media sources to external drives.

It's disappointing but not surprising to learn Skin Helper is the mastermind behind all of this. I never really been a huge fan of that script. It's caused problem in the in the past.

Thanks @latts9923 once again your excellent detective skills and intimate knowledge of this skin has answered my questions and I'm confident with what is learned from this post MB1968 and others with be well on their way to solving their artist artwork issues. 

Bravo.