Just looked under the light panel and there's nothing but the harness for the lights and the rear seat tilt controls.

I'm just guessing, but did the DVD/VCR live under the trunk boards, with power coming from the 4-pin plug in the last photo, a remote wire (also in the last photo) and then the video and audio outs plugged into the silver module? The only thing I can't understand is how you'd control the player ie: start, stop, FF etc.