For Windows cloud server, you can re-image to another Windows cloud server of same or different version.
For Linux cloud server, you can re-image to another Linux cloud server of same or different distribution/version.
You would not be able to switch from Windows to Linux or vice versa. If you need to change operating system, you would need to add a new server and unsubscribe the existing server.
** Please be absolutely sure before take the action to re-image your server as it will destroy all existing data on the server. Re-image server action will destroy your current server and create a brand new one base on your new choice. Ensure that you backup the data that you want to retain before proceeding.
For guide on how to re-image your cloud server, please refer to the related article below.