Google announced this week that the stable version of Chrome OS is currently in the process of being updated. This update will bring the stable channel up to version 61 (61.0.3163.113) and with it will bring with it a number of improvements, both at the visual level, and under the hood. For reference, Chrome OS is the latest platform to receive the update to version 61 following the update's arrival on Android and on desktop back in September.
The changelog for this update is not that long but does state that the default avatar and picker have undergone a design change. Which also seems to be the case for the app launcher. So both the general view of the app window, as well as the user avatar will appear different after updating. Likewise, there is also a new Sign in and Lock Screen design with this update, so expect to see this change once the Chromebook is booted up for the first time after updating. As for the under the hood changes, these mainly come in the form of improvements to the window management support for when a Chromebook is used in tablet mode, and improvements to the power management setting in general. Although the changelog also does note (without going into specifics) that the Get Help app has been improved with this update as well.
While the update is now confirmed as in the process of rolling out, it is expected to take a few days before the rollout is complete, the blog posting went live yesterday and therefore it should have already arrived on a number of Chrome OS devices. Speaking of which, and in spite of this update rolling out to the stable channel, the blog posting does note that not all Chrome OS devices will be getting the update, although most will. For example, a number of Acer options (including the Chromebook 11, the Chromebook 14, and the Chromebook Flip) wont. Neither will, the Chromebook Pixel, Dell's Chromebook 13, Lenovo's Flex 11 and N23 Chromebook, or Samsung's Chromebook Plus and Chromebook Pro for that matter. And these are just a few of the devices listed as not receiving this update at the moment. The full list of non-supported Chrome OS devices available through the link below.