Q. Is there a graphic tool to help create Nano Server images?
A. On the Windows Server 2016 media is a folder called NanoServer. This has a PowerShell module that is used to create custom Nano Server images (as I documented at http://windowsitpro.com/windows-server-2016/create-new-nano-server-image-2016-rtm). There is also a graphical tool available for download from https://www.microsoft.com/en-us/download/details.aspx?id=54065. The tool requires the installation of the Deployment Tools and Windows PE from the Windows Assessment and Deployment Kit. Once installed the process is completely wizard driven and create both VHD files and also bootable USB drives to enable Nano Server deployment to physical servers.
Just like a regular Nano Server image creation you must point the tool to the Windows Server 2016 media where it can access the Nano Server WIM file and list of packages. Microsoft has a full blog post on the tool at https://blogs.technet.microsoft.com/nanoserver/2016/10/15/introducing-the-nano-server-image-builder/.