Some improvement with 1643, but not quite there yet ?
The keywords "inlay" and "back" ---> Cover (back) : OK
The keyword "front ---> Cover (front) : OK
The keyword "Leaflet" and all other .jpg-files (?) ---> Media Label : This seems not OK

[url=http://en.wikipedia.org/wiki/ID3#ID3v2_Embedded_Image_Extension]ID3v2 Embedded Image Extensions[/url]:
$06 Media (e.g. label side of CD)
This means the label on the disc itself.

In case you made the decision not to implement keywords for all types of the ID3v2 Embedded Image Extension
(that are available in the pulldown list of the artwork properties)
wouldn't it make more sense to use the type "other":
$00 Other

Hoping not to annoy you guys.. ;-)

Ok, will be fixed in build 1643 as http://www.ventismedia.com/mantis/view.php?id=10978

Technically speaking, in case of the typical jewelcase, the "Inlay" means something different from the booklet (leaflet):

[url=http://www.bizreplication.com/frontlinertemplate.htm]Jewel Case Front Booklet Art Template[/url]
[url=http://www.bizreplication.com/inlay_template.htm]Jewel Case Tray Card / Inlay Card Template[/url]

Furthermore, the [url=http://en.wikipedia.org/wiki/ID3#ID3v2_Embedded_Image_Extension]ID3v2 Embedded Image Extensions[/url] do not differentiate between "back" and "inlay",
but certainly between "back" and "leaflet page".
To me it seems rather plausible to link inlay-images to the type "Cover (back)",
because every inlay image is also a back cover image (although not vice versa).
---
I am stumbling on this right now, because I am reorganizing all of my linked album art, following naming patterns like those mentioned in the first post.
In case that album art and audiofiles get mixed up by accident it will be possible to identify the images by filenames alone.
It would be very convenient to have MM consistently recognize cover types by keywords in the images filenames.

I see in the code that words 'INLAY', 'INSIDE', 'BOOK' results in 'Leaflet Page'

You seem to be true that we should probably add 'LEAFLET' to the detection, but I am not sure about removing the 'INLAY' because it looks like it was intended/designed this way.

MM seems to identify [b]some[/b] cover types in album folders by [b]wrong keywords[/b] when scanning for album art?
Working fine are the keywords "front" and "back":
Hilliard Ensemble - Machaut, Messe de Notre Dame - back.jpg --> Cover (back)
Back - Hilliard Ensemble - Machaut, Messe de Notre Dame.jpg --> Cover (back)
Front - Hilliard Ensemble - Machaut, Messe de Notre Dame.jpg --> Cover (front) ...etc.

But the keyword "Inlay" seems to be wrongly connected to "Leaflet Page":

Hilliard Ensemble - Machaut, Messe de Notre Dame - inlay.jpg --> Leaflet Page
Inlay - Hilliard Ensemble - Machaut, Messe de Notre Dame.jpg --> Leaflet Page

While the keywords "Leaflet", "Leaflet Page" etc. lead to cover type "Not specified":
Leaflet - Hilliard Ensemble - Machaut, Messe de Notre Dame.jpg --> Not specified

It would be nice to have keywords for all of them available.