Arcade Demo screens from Arcade machines are awesome.

They give you a taste of the game, and entice you to play, even if you are just glancing over.

Doing something like this in steam could be tricky and/or clunky but hear me out.

Baseline functionality:

Allow users to create playlists from one or more videos or screenshots from a game's store page. Optionally including their own screenshot/recording gallery or community media.

Allow for creating playlists of playlists (one per game). Think cycling through the 4 options on a neo geo Arcade game demo.

Surface a (Press enter/steam button to launch) context option to launch the associated game.

Once this gains popularity, Allow steam game developers to add their own Demo reel defaults pre-included.