Securing System Monitoring wall display PCs

I have several windows machines which drive dashboards on wall mounted displays for system and network monitoring. I would like to be able to secure them from unauthorized access or modification. Currently they have an unprivileged account, it still has some access, which is a foot in the door.

In my mind, the ideal solution would be something like locking the machine with WindowsKey+L, but the screensaver still shows the screen contents. I have not been able to find anything to do this, that keeps the screen updated. I assume this is due to the underlying architecture of windows. All solutions I have seen so far mentioned do not protect against someone connecting a keyboard, pressing Ctrl+Alt+Del and subverting the security measures. So far, the only way I have seen is to physically secure access to the machine that is driving the display.

Does anyone have any suggestions on how to best secure network monitor dashboards Machines. Access is still needed to modify the display or settings and change layout, but this needs to be authenticated and as secure as possible.