An updated image of the Steam Controller has appeared in the latest Steam client beta. It's actually not all that terribly different from the one that turned up in July, although it appears somewhat more compact, and now has a directional guide on the left thumbpad.
The controller still boasts the analog stick that was added over the summer, but it also looks slightly narrower, and the shoulder bumpers seem to be rounded down just a bit. The only obvious change is the directional indicator, which ValveTime says could indicate that the left pad might provide a "softer, more diverse alternative" to standard D-pads, with more than just four points of movement.
The fact that the design hasn't changed much over the past half-year suggests that Valve has settled into a design it likes, and is now deep into the refinement stage. The timing would make sense: Valve hasn't made any official announcements about the controller, but it did tell TechRadar in November that it will have a "large Steam Machine presence" at the 2015 Game Developers Conference, which takes place in early March.
To get a look at the new Steam Controller diagram yourself, first ensure you're taking part in the Steam client beta program, and then check your Steam/tenfoot/resource/images/library/controller directory.
