I think that you are true anyway, getFirstImageURL() should work also with dynamic albums.
I possibly found a bug in getImage($index) function in album class-album.php:
`return newImage($album, $images['filename']);`
should be:
`return newImage($album, $images[$index]['filename']);`
If not I get an Undefined index notice when I call it from getFirstImageURL() while in dynamic album context.
Then the URL in getFirstImageURL() function should be modified for dynamic albums to have a link to the right static album containing the image.
May be I'm going beyond my knowlege and my possibilities, if so be patient with me please