Compatible with Nightingale
It appears as a fetcher on the Artwork options panel and can be prioritized, enabled and disabled as required. (You may need to tick 'Auto-fetch Album Artwork' on the Artwork options screen to see album art!)
Track Art Fetcher optionally returns:
1) the media item's primary image (set by drag-and-drop/pasting an image on the metadata editor or the Artwork display pane); and/or
2) art from the track's directory (either all or files containing the track's file name) with file extension in the list on the Track Art Fetcher preferences.)
It works with all add-ins that use Album Art fetchers. However, as far as I am aware, only NowPlayingArt displays multiple images for a track.
Version 1.8 now handles web art in the primary image property.
Please report any problems to me at Songbird.TrackArtFetcher@gmail.com.