Enable Designing of Controls Themes

When I drop a Controls Button on the canvas there's no good way to define the backgrounds in the Designer. I often see people creating invisible Rectangles by hand in the Background property to avoid the theming and then there are several ways they create the backgrounds. All end up requiring a bunch of property bindings or else state configuration. This feels like a prime area for improvement.

A couple of ideas that come to mind.

1. Enable file import that creates Imagine Style naming.
2. Assume Button types will use Images and enable specification of background sources for each Button state.