Samsung has pushed out an update to the Always On Display functionality on the Galaxy S7 and Galaxy S7 edge, bringing new customization options. The update replaces the two existing calendar themes with a single calendar, and you can now set any image on the device as the AOD background through one of the new clock options. There's another new clock that lets you add a text signature right below the displayed time, with the ability to customize the text's font as well.
Sadly, the update doesn't enable third-party app notifications, but we're guessing the feature will arrive with Android 7.0 Nougat, which will bring the Note 7's Grace UX to the S7 and S7 edge. You do, however, get the option to display the currently playing music track (this works with any app that can play music). Samsung has also optimized battery usage – the company claims that AOD will now use less than 1 percent of battery every hour. The changelog does note that this figure is based on Samsung's internal measurements and your mileage will vary based on your chosen AOD content.
The Always On Display update can be grabbed from the Galaxy Apps store, and also from the Always On Display menu in Settings » Display (just go into the AOD menu, hit About Always On Display, then hit the Update button).