What is "offline"? Do mean you to perform a sysprep, where you logon to Windows and interactively run commands to update the system, before capturing the install image? Or do you want to automate the running of installers during Post-Setup?
There are a number of online guides on how to do a sysprep. You can spend as much time pre-installing software and making customizations. When the ISO image is replaced by your capture image, Windows has been "pre-loaded". But if you get a new base version of Windows, then you have to repeat the entire sysprep operation from the beginning.