According to Google’s Wayne Piekarski, “We are working to make this as simple as possible for you so that it’s easy to make good-looking faces that work well across multiple form factors, conserve battery, and display the user’s card stream nicely. Some of these changes won’t be ready until we migrate Android Wear to the Android L release later this year, but don’t fret: they’re coming!”
We should note that the customizability will be limited to the watch face. Earlier Google had stated that they will be maintaining control over the UI of Android Wear. This is to prevent OEMs from going too overboard with their designs, which is what is happening with Android phones at the moment.
While customizability is a great feature and one of the features that many criticize Apple over, it can sometimes bring a bad experience, which in turn might cause the user to associate that with Android in general. In any case if you had your eye on an Android Wear device, we guess custom watch faces is something you can look forward to in the future!