Images found by SteamDB in a sub-folder of the latest Steam client beta, which we've confirmed the presence of after updating our own clients, depict an overhauled Steam design with new sections for apps, comics, TV, movies, and music.
Steam has already dabbled in selling non-game software and movies, as well as soundtracks bundled as DLC, but up till now these categories have played second string to games. The mock-up, which you can see above, integrates them into the main nav where we'd normally see 'Library,' and introduces comics and TV as major new categories.
The inclusion of Halo 5: Guardians in the games list on the left (enlarge the image above to see) speaks to how much of a placeholder this image is. Some of the game icon choices, like the now-defunct Evolve and eight-year-old Mirror's Edge, are also strange, further suggesting this is just an artist's vision. It may not even be a Valve artist's vision, but something an employee downloaded.
The image at the bottom of this article was also found in the client beta with the name SteamU_details_34_nomarkup.png. It looks like a mock-up for a new game page format, though the bit in the middle is an existing page detailing Dota 2's Dark Rift update from last summer. I assume 'SteamU' refers to Steam Universe, a term Valve has used to describe SteamOS and Valve hardware.
The most interesting element is at the bottom of the image, where we can see a partially obscured Windows desktop with an open browser. Two observations: The date in the taskbar is 12/7/2016, and whoever owns this desktop recently downloaded netflix_master_sign-in.gif. That image could be this mock-up by a non-Valve designer. Inspiration? It's too thin to make any conclusions, but I wouldn't be surprised to find out that Valve wants to integrate movie and TV streaming apps into Steam for use on SteamOS, in Big Picture Mode, and in VR.
We've reached out to Valve for comment, and will update this post if we hear back.
Update: According to SteamDB, Valve has released a new beta build to remove the files—which only confirms the obvious, that their inclusion was a mistake. Regardless, the images could easily be the musings of an internal or external graphic designer, and not representative of future plans (we wonder if they could have come from a candidate Valve was considering hiring). We'll stay curious but skeptical until Valve confirms anything one way or another.