In MadMapper we can't directly map the DMX fixtures on a media, but we can use as media the video output of a MadMapper projector through Syphon (macOS) or Spout (Windows).

Then you can do video compositing on your fixtures and have a better overview of your show in your previews.

Here's a useful video explaining the steps : DEMO Syphon/Spout Loopback on LEDs with MadMapper 3