SQL Server 2016 is barely 6 weeks old, and so but the AdventureWorks sample databases have yet to be released. However, one thing that is available is the CTP3 databases from back in December 2015. The sample scripts cover many of the new features, including JSON objects, Row Level Security and StretchDB, amongst others.
But Microsoft have released a new sample database called WorldWideImporters available on GitHub. There’s bacpacs for SQL Azure, an Ispac for SSIS, and baks for SQL Server 2016. There’s sample scripts for PolyBase, Always Encrypted and other new and exciting new features.