Artwork missing in Live Tile / Growls only

[Dimitri]

My artwork is embedded in my .wma files and does show up in the app itself when I'm using / browsing it.

However, it doesn't display in the tiles, and the notifications only show the default MM icon instead of the artwork (such as when I'm changing volume).
Also, there's nothing showing on my lock screen even though it is selected in the PC Settings.

This used to work. I'm running Windows 8.1 preview now.

[PetrCBR]

This was reported several times and we're preparing big update.