What would be a good UI design for a form to pick randomly several items on the left list, that link to the selected item on the right list, and just as conveniently select several on the right to link to one selected on the left? Like a mover with a joiner in between.

The trick is length of the list on one side and the fuzzy information on the other, say lists of animals and lists of pictures with animals. Pick a bird and a horse and a dog and pick pictures with a bird and a horse and a dog.

Any examples of that out there?

Thanks,

Al Allison