Preview at WWDC likely in June, followed by September launch.
Apple Watch Hacked to Display Custom Watch Faces
In a tweet posted this afternoon, Sood shared a video of a custom animated watch face with multiple color options.
The watch face source code that was used to create the custom watch face has been made available on GitHub and will require watchOS 2. Earlier this summer, Sood also joined several other developers in efforts to hack watchOS 2 to run truly native apps like Canabalt and a Flappy Bird clone.
It is not clear if Apple has plans to allow third-party developers to create watch faces for the Apple Watch in the future, but it's possible that as watchOS and the Apple Watch mature, Apple will be less restrictive. For now, hacks like Sood's are the only way to get custom watch faces on the device.