SQL Server 2012 RTM sample databases are available at codeplex

http://msftdbprodsamples.codeplex.com/releases/view/55330
Installation instructions
http://social.technet.microsoft.com/wiki/contents/articles/3735.sql-server-samples-readme.aspx
Download Center:
Power View and PowerPivot HelloWorldPicnic Samples for SQL Server 2012
Image Files for HelloWorldPicnic Sample Model in PowerPivot and Power View