Yesterday Microsoft published the Windows Server 2016 Technical Preview 2 bits
During the installation process, you have two options, installating Windows Server TP2 with local admin tools or without.
Even if you choose with local admin tools, at the end, you will have not have the full GUI experience, as Microsoft is trying to reduce the OS footprint to the minimal.
If you definitively want to get the full GUI installed, go to Add and Features Wizard, Select Features and under User Interfaces and Instratucre, check Server Graphical Shell.
Confirm the installation.
A restart later, voilà J