It looks like Fallout and seems to taste like Fallout (although that might just mean my monitor tastes like Fallout—which is... ominous), but it's not Fallout. CreepBOOM made this gorgeously mournful piece in Garry's Mod, along with copious others.
Here are a few Garry's Mod shots based on the excellent STALKER Chernobyl survival FPS series, evidently one of CreepBOOM's favorites:
And here are a couple based on Metro 2033, STALKER's close (albeit significantly more linear and, er, underground) cousin:
Half-Life 2, anyone? Some great use of color, camera position, and lighting here.
And lastly, to get away from all the post-apocalyptic gloom, here's a nice shot that's simply titled "Weekends."
The Steam Community Showcase is a regular look at the cream of the Steam community's boundless crop. Art, videos, guides—whatever. Each installment highlights a specific piece or person. If you find anything cool on Steam or would like to have your work featured, drop me a line.