VDI golden images allow to deploy several virtual desktops based on a single base image. This configuration simplifies a lot desktop management but also complicates updates.
A VDI golden image contains an operating system and hardware configuration. Windows-based images can be managed using Microsoft Sysprep tool in order to clone the OS. The image usually contains also patches and applications, but applications can be also virtualized separately.
One of the advantages for IT admins is that golden images can be configured to adhere to corporate security and compliance requirements, hence ensuring all virtual desktops generated by the image adhere to those policies too.
Some organizations don't have a standard desktop configuration, since they may have different user profiles with different requirements. In these cases they should maintain multiple golden images. It is recommended to limit the number of golden images to make it easier for IT to manage.
Updating golden images is the most trickier task, because usually there is a patch to apply or a configuration to be changed. In many cases, updating a golden image doesn't mean the virtual desktops based on that image are automatically updated even syncing the changes.
In some cases, when changes are synchronized, new virtual desktops are generated based on the updated base image. But if we're using persistent desktops, this process can't be performed, since all user data and configurations would be deleted. Thus, admins may have to update persistent virtual desktops individually. A useful tip in these cases is is to apply several updates at a time, to regenerate desktops a single time instead of each time an update is applied.
Finally, you should bear in mind that a wrong golden image configuration will affect all virtual desktops, so you should always test updated golden images before generating new virtual desktops.