Another image of the Metro UI for Windows 8 have also now surfaced on the Internet. The image shows the back, forward, close, minimize, expand, help, and several other images that Microsoft will incorporate into, most likely, the 'Aero Lite'.
This theme is expected to be used by users whose computers don't have the specs to run a dynamic interface. Microsoft knows that Windows 8 will be used on older hardware and wants to maintain its Metro design language across all themes that end users might use. It's not known at this time if there will be the 'classic' option theme in Windows 8.