So, you want a little more variety than what Apple has to offer for watch faces. And, you want them to be more personal than the specially designed images that Apple Faces provides. But you don't like using any old picture from your Photo library without being able to give it a little more Apple Watch-i-ness.
Watch Faces is a customizable photo app that specializes in making images for Apple Watch. You can use whatever photo you want, and with customizable layers, you can turn a random photo into an Apple Watch face.