Valve is currently working on two already announced games; Portal 2, due out next month and DOTA 2, due out sometime in 2011. But Valve is likely working on other games as well. During a recent visit to the game developer's offices, a Team Fortress 2 community member, "Political Gamer" took some photos of what he saw and posted links on the Steam message boards.
One photo was an image of some concept artwork on a wall that, well, doesn't look like anything we have seen before. It doesn't appear to fit with either Portal 2 or DOTA 2. Perhaps it's something akin to the long awaited Half-Life 2: Episode 3? "Political Gamer" posts later in the message board thread that, "those pictures are just some art done by people at Valve." But they clearly seems to be for game development. So let the speculation begin.
[Via PC Gamer]