I guess this tool could be significantly better if the image to be used could be specified by editors of the article that is linked to. Those could then also be used in other places, for example category pages could be made to show images if that makes sense.
W:en:WP:POP (hope I am linking to this correctly) has a feature where it displays a popup with the start of the article plus an image, and the automatically chosen image is often not a very good choice. A way to mark an image would also help that tool.