James did a great video awhile back, "Changing Your Design In Detail". It covers both themes and widgets. I use it a lot! It's a bit dated now, so thanks for the great new video on Widgets! Anyway you could do one on themes?
I suppose you may be waiting for the new Pro Blogs to come out as it would be great to show accessing the supporter/premium themes link. Tough call - since it's super admin defined what would be a good generic name? My vote would be with "Premium". Seems to be a common term for feature rich themes.