Great move for consumers and devs. Now, let's add the ability to submit videos of apps in action or app trailers (with the same review process).
Boost and promote good devs, the rest will follow.
They should develop some code based way to do all that - screenshots and yeah maybe video snippets. You want this screen to be available on the app store, make the code calls. If the app gets updated, that screenshot or video would update via a code cascade of whatever visual assets would be onscreen at that time.
That way it's 100% verified that it is an accurate screenshot, not doctored, not a poster. If a company wants to add captions or metadata to the images/videos, they can do that. But absolutely forbid dorky posters and require actual screens.