I'm still fairly new to roll20, started out as a GM and I originally just dragged everything from my folder on my computer to the tabletop. This however apparently flooded multiple images into my library every time I did this and now if I were to clean up my library I would lose tokens that have important data for me.
My suggestions are as follows:
1) Allow the ability to reassign token images to others in the library.
2) When browsing your library, have the information available for what pages/handouts/journal entries are associated with said token.
3) If an identical file is uploaded, automatically link it to the previous incarnation of the file in the library and don't make it as a new image to take up that space.