Plugins can already have multiple thumbnails uploaded, and the page certainly would benefit from having a slideshow like the game pages have that can show off a lot of features.
Video thumbnails could give the players a quick preview of what the plugin does and how it’s used.
I was thinking about this when I uploaded my first plugin. I wanted to have my own smancy logo/icon to identify my plugin, but I also wanted to provide a preview. I can only do one and having a preview doesn’t make a good icon in the catalog.