While you could always install different themes on your Android device, you have to rely on third-party apps for that. It wasn’t until the Android 10 release that Google finally took advantage of the robust theming system from the Android Open Source Project (AOSP 10) and brought the Pixel Themes app to the Pixel Launcher. Now it looks like they will be adding more customized items to your phones, well, if you own a Pixel device. Android 12 will reportedly bring Pixel-exclusive lock screen clocks.
XDA Developers shares that two years ago, Google was already working on 3 lock screen clock presets: a text clock, a bubble clock, and a stretch analog clock. But for some reason, they eventually removed it from the SystemUI app. Before the drop of the first Android 12 Developer Preview, XDA said that the new layout and enlarged clock of the new UI for the lock screen is possibly to make it easier to swap the default clock for other digital clock offerings they may have.
They discovered a new code in WallpaperPicker app in Android 12 that is related to custom lock screen clocks. Basically, it looks like Google is working on something that will give users the option to change their lock screen locks but it will only be preinstalled exclusively on Pixel smartphones. Obviously, the device will have to be running on Android 12, although currently, this package is not yet in the first Developer Preview released.
There’s a possibility that this will show up in Developer Preview updates although there’s no guarantee that it will show up before the stable version of Android 12 releases later this year. In any case, there will probably be a lot of UI changes that will come with the latest Android update so even if custom lock screen clocks don’t show up, there will be other things to catch your attention, at least UI wise.
So far, the code indicates that this will be for Pixel devices only but there’s also an open-source version of the feature. However, it will most likely be up to your OEM to develop clock faces exclusive to your device brand.