I made my own version of the Default theme that's closer to Windows 8's UI
Hello! I made a replacement for the PortableApps.com Menu's default theme, to make it look more like Windows 8. To install it, extract the "Default" folder from the zip, and (after backing up the original,) move the folder to X:\PortableApps\PortableApps.com\App\Graphics\Themes, and overwrite the original. The theme has most of the background colors replaced with ones that are closer to Windows 8, too, so be sure to check them all out! Other than the scroll icons, none of the icons are replaced.