I wish I had a theme that cycled through some cool nature backgrounds while having notification sounds that of nature sounds. However, I've only been able to identify one or two themes through www.windows.com that have custom sounds. Is there another way, or are they just unsupported?
You can still create, assign your own sounds in W8 with the old desktop control panel. Just look for the Personalization icon, then the 'sounds' at the bottom of the screen. From there you can change sounds to your heart's content. (You just need to have the sound files already download)