Q. Can I add features post Nano server creation?

A. Technically yes however its not very pretty right now however this may improve over time. This is because the neutral binaries and the language files are separate cabs. Ideally you would simply recreate the Nano server image with the features required. If you need to add to an existing Nano deployment the best way is to create an unattend file and pass that to DISM. The best example of doing this approach is documented at https://msdn.microsoft.com/en-us/library/mt627783.aspx for IIS however this should be on an exception basis. The point of Nano server is they are cattle and you don't spend time reconfiguring. You shoot it and create a new one :-) http://windowsitpro.com/windows/pets-and-cattle-methods-deploying-cloud-services.