Exchange 2007 came with four built-in themes and a flexibility to customize as well. Seattle Sky, Xbox 360, Zune and Carbon Black. Well, the settings are the same in Exchange 2010, but users can no longer change the theme. The option to change the theme within OWA is missing and Microsoft has confirmed that the feature is not available in this release.
In OWA 2007, you could change the theme to the one of your choice (if it is allowed by the admin in the first place), by navigating to Options –> General Settings –> Appearance Section.
Link – http://www.howexchangeworks.com/2009/09/themes-in-outlook-web-app-owa-2010.html
