Here's the help file from Micros:
More Media Files
Supported media files include Midi, Avi, Mp3, and Wav file types, subject to limitations of the device’s operating system. For example, since WS4s have no sound output, they do not support Avi files and will not play the sound portion of other media.
Media files must be placed in a \micros\…\media folder on the local workstation where they are to be played. To support training mode, a file of the same name can be placed in the \micros\…trainingmedia folder. The system will determine which file to play, based on the status of the signed-in employee.
If a media file with this name is not found in the appropriate folder, the system will ignore the option.
I'd be careful about using this on CE workstations, (WS4, WS5 & WS5a). Media files are pretty big and will chew up the memory pretty fast.