Here is a list of items that are tested in your Windows 8 App. If you are in Southern California, please email these posts for more information on getting a token for your app by June 30, 2012!

.Metro style design emphasizes content over chrome, emphasize cleanliness and doing more with less. Following these principles will give you consistency with other apps, but you should not lose sight of your brand; design your Metro style app to promote your brand and accomplish a purpose.
Think about the message you want to send your users when they see your Metro style app in the store, when they see it on their Start screen, when they first launch it, and when they are using it. Take advantage of these opportunities to define and promote your brand in the visual design of your app.
The branding section of the planning your Metro style app in the Windows developer center has great tips for letting your brand shine through to your users.

Reference (HTML)

http://msdn.microsoft.com/en-us/library/windows/apps/hh465418.aspx

Reference (XAML)

http://msdn.microsoft.com/en-us/library/windows/apps/hh465418.aspx