You can use third-party tools to achieve your requirement but I doubt whether this can be done with native windows tools like GPO.
Group Policy allows you to enforce only one wallpaper for each user, so if you're looking to announce several events at once , all announcements will have to be placed on a single image
Another factor is that to apply the Group Policy and enable the new wallpaper, you will need to restart all of the computers involved or find a way to make all users do it.
To set a group wallpaper for all users in Active Directory you need to access the Users and Computer settings, click on the domain name and choose ‘properties’. From here you will find group policy tabs that will allow you to send a wallpaper to all computers and disable users from being able to change wallpaper.
Hope this resolves your Query !!
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