Right now your only options are what's on the watch. Who knows what the future will bring.
I have a feeling that once Apple has released the SDK, as well as their (most likely) strict rules on how to design new watch faces we'll start seeing new custom, third party watch faces. It would be incredibly stupid of them to limit this device to the 10 faces they currently have, especially when they could probably license/sell some of them (like Disney character ones) and also the fact that customizable faces are one of the big/only draws of the android smart watches right now.