Valve is rumored to be working on an open-world game called Stars of Barathrum, which takes place in space.
This is according to the gaming forum Facepunch, which claims the images posted on the forum are from the game.
The site says players will be able to pilot various ships, and it's large and ambitious in scope, and "plays like privateer/freelancer," and contains "a vast and open-world where you choose your own adventure."
The concept art posted was created by Peter König, an ex-Valve employee from 2008 until this year.
Take all of this with a grain of salt, says Gaming Bolt, and we agree with them.
König has worked as a freelance artist since leaving Valve, so his artwork could be from or for anything. So, yeah.
This isn't the first time concept art has surfaced as you see in the video below from February.