Download the ChangeScreenResolution and save it on a client PC.
How to use it:
On the webadmin, go to Settings > Client Configuration > Add a Startup Command.
In the Command field enter: ChangeScreenResolution.exe
On the parameters field, enter the desired resolution, and refresh rate (do not include them if u want to use the default)
/w=1920 /h=1080 /f=240 /force
/w = width (optional)
/h = height (optional)
/f = refresh rate (optional)
/force = command to force these settings (required)
In the Working Directory field, enter the path where the ChangeScreenResolution.exe is located. (do not include ChangeScreenResolution.exe)
Enable long running
Enable hide process
Superclient a client PC, start it up until you see the UI. (The 1st startup will not execute it but it should save the configurations.)
Restart the client PC, and this should execute the startup command.
Turn off the client PC and save the Image.