I had the same problem in the darker areas of Minimicus. I needed them brighter, but adding light entities wasn't the right solution and Map Brightness didn't work for me either. I was able to get the right amount of light by using the -ambient parm in the $light.exe compile command. I set mine to -ambient .0047 .0047 .0047 which barely lights up the dark areas. Try a higher setting if you need more light. The settings are very sensitive though, as you'll discover if you try it.