As a convenience to readers I'm listing the download links to the Microsoft sites below - I'll update this post if any more become available (and when I find them - there is a "Watercolor" XP beta theme lurking around somewhere but I can't seem to find a Microsoft signed copy).
|Zune||Orange and black|
|Windows Embedded||Dark blue|
|Royale||Shiny blue Windows Media Center (note Microsoft removed the official link here and replaced it with just the wallpapers).|
|Royale Noir||(Incomplete black theme NOT compatible if you have standard Royale - read the linked page first!)|
Update: I've just found out Viperfang covered all of these with screenshots a few weeks ago - have a look