I have ideas, but not a fully formed concept. Searchable keywords, frame notes, dates, artist, and other attributes would be a great help. A screen with large frame icons is very important, since visual search is the most natural.
In the past, when I created new songs that use frames from past shows I used Showtime to load up several different frame files. I drag the blocks of frames I want to keep onto the timeline, then use the 'delete unused frames' function to condense the frame file. But this system relies on my knowledge of what frames were used in past shows.
Ideally there could be a database system that organizes and tags all of the frames on a computer. You'd be able to refine search terms and scroll through thumbnails. Then easily drag and drop frames into 'albums' or 'collections' as well as into your new project.
It should be simple to add keywords or other markers to large groups of frames. Because tagging old frames with info is the only way to make them easily searchable. It also makes sense to have a comparison system that can help weed out redundant frames that are repeatedly used in several shows.
Stock photography sites like istockphoto.com or other photo and video organizing programs are good to use as reference.