You've been asking for it for a while now, authors, and Dolby has finally had the time to implement it:
You can now set the display order of the images. Thumbnails will be selected by either the lowest display order number or the earliest image date if there is no display order set.
Very nice. Now if only some of the authors would make use of it... I hate seeing the compilations with a screenshot of their folder list instead of an actual shot of their UI in the mouseover.