Star War’s iconic lighting panels embedded into the walls of the Empire’s cruisers and Death Star apparently originated when the director of photography Gilbert Taylor found the original set designs by John Barry to be “like a coal mine – all black and grey with no opportunity for lighting”.  The change to lighting panels chopped into the set pieces had the side benefit of allowing Lucas to shoot in any direction with constant relighting.

The following retrospective video discusses the change at 15:07.