This is great for somebody who has the color sense to be able to assign values to all the different design elements and have it assemble into a coherent whole (and the time to do that). Better for the rest of us would be a selection of completed themes and the ability to change individual design elements.
There is already a selection of completed themes within eM Client, and this new editor gives you the opportunity to change individual design elements in those themes.
Found it. Thanks. 20 chars.