That's because at first glance, Android Auto 6.0 doesn’t include any big new features, though we do know of several important improvements already being planned and likely just around the corner.
One of them is support for wallpapers, something that Google has been working on for quite a while and supposed to go live rather sooner than later.
With wallpaper support, Android Auto will allow users to choose a background for the home screen, though it's worth knowing that Google won’t just make it possible to select any custom photo for the whole thing. Not at first, at least, so users will have to pick from a pre-loaded collection of wallpapers that will come bundled with Android Auto.
These images are already there in Android Auto, including in this newly-released version 6.0, only that the feature isn’t ready for prime time; we just have to wait a bit more until Google enables it. When the development phase is finalized, the new feature will show up in Android Auto’s settings screen, allowing you to choose a new wallpaper on the fly.
Google has never commented on wallpaper support coming to Android Auto, so no ETA has ever been provided for this feature. It is, however, expected to land in the next few updates.