It appears Valve has revised its Steam Controller with an analog thumbstick.
This is according to a diagram of a new design found within the July 23 update to the Steam client beta by SteamDB.
As you can see in the image posted above, the directional buttons originally on the left were removed and replaced with the thumbstick.
While the image isn't actual confirmation of a design switch, those who prefer a controller with a thumbstick will like the additional option alongside the trackpad.
If are part of the Steam client beta, PC Gamer says you can find it in the Steam\tenfoot\resource\images\library folder.
A look at how the controller looked a month ago is posted below for comparison purposes. But, it's been said there are customizable configurations at this point, but it's unknown if that will be an option at release or not - we'll have to wait and see once Valve is finished with the peripheral.