I would strongly disagree with this. While it seems to be a popular myth that the lights where not infact 'ON' in ROTJ, they most certainly were. The reason why they appear off is that the lights are washed out. However, in the following HD captures provided by Art, you can make out the faint hint of the red glow of the lights (you have too look close for it).
As to what was the display, the answer is 'Unknown', but speculated to be the exact same display as see in ESB production photos