
The premium version (costs $3.99) of the WatchMaker app for Android smartphones comes with plenty of high-quality watchfaces with full customizability. It also offers an ability to create custom watchfaces from scratch. There's also a Google+ community where users share their own watchfaces with others.
The company has mentioned that current premium users of the service can use all their watchfaces on the Gear S2 and the Gear S3 without any extra charge.