Samsung Galaxy S7 in 2016), you now have 30 new clock styles to choose from for the AOD feature. First, you will have to sideload (for now) a new official app from Samsung on your device that is aptly named "ClockFace." The app requires your phone to have Android Oreo installed along with Samsung Experience 9.0.
ClockFace offers you the option of choosing different clock styles not only for the AOD display, but also for the lock screen. You can change the color of the clockface you select, or have the color change based on the lock screen wallpaper you have up. The clock styles available include both analog and digital options, and some show the day and date. You can view a few of the available choices by checking out the screenshot of the app that accompanies this article. All 30 options can be seen by clicking on the slideshow below.
While the app is from Samsung, the company has not yet added it to the Galaxy Apps Store. That means that you will have to sideload it from APK Mirror. All you need to do is click on this link and follow the directions. Once the app is installed, go to Settings > Lock Screen And Security > Clock And FaceWidgets > Clock Style.