You should probably look at the Intel AMT SDK documentation to see all the options that are avaialble in the "RemoteCommand" method of Intel AMT. The custom command dialog box of Intel AMT Terminal allows a user to set all of the parameters for that call. What is allowed changes depending on the computer you are using and so, you have to see what options are allowed on the dialog and test them out.
In general, most users would use the basic remote control features such as "Power on", "Reset"... The custom commands are very useful for testers and developers.
Ylian (Intel AMT Blog)