My opinion isn't worth much as I'm not capable of adding such things myself, but seems to me it might be better to come at it from the other end - that is, gradually expanding the functionality of the pictureflow plug-in, rather than adding art to the database browser.
If one could add more options to pictureflow, to, for example, allow you to view covers as flat thumbnails (sliding sideways) as well as the forced-perspective rotating view that it currently uses, or to view them as a vertically-scrollable list accompanied by the album name, one could, maybe, gradually subsume many of the functions of the database view into pictureflow?