No images for subtroped pages?

This issue came up in recent discussions on the Image Pickin' forum. In one of the threads Septimus noted that there is a rule that "medium-specific images should not be placed on the medium-agnostic main page". We are now in the process of reverting the image updates for the main pages of Driven to Suicide and Big Eater which is unfortunate.

How did this rule come about? I don't see how this serves us in any way. E.g., what good is an appropriate illustration under Manga, if one is heading from the imageless main page to the imageless Western Animation subpage? The illustration should be with the description to get the idea. Stuffing additional images on the example pages is a nice to have but of less importance as far as I am concerned.

I'm of the opinion that if there is only one image for all subpages, it's fine if it's on the main page. Also, if one image falls into several media categories somehow, or at least doesn't clearly fall into one of the subpages, it's also fine.

This was put in place at least a year ago, if not longer. The gist, IIRC, was that for pages that have grown big enough to be subpaged, and more than one good image can be found for the trope in multiple media, it's better to use those pics on the subpages rather than trying to figure out which one to use for the main page.

Another Duck does have a good idea about keeping a pic on the main page if only one good one can be had at the time...I can live with that as a compromise, with pics being moved to subpages later on if good pics from other media are found.

How is choosing the one best image for the main page and leaving the others on subpages any different than what we do for a non-subpaged trope—choosing one image for the main page and leaving any other options on Image Links?