direct light 0 0 0 ambient light 0 0 0 shadow light 0 0 0
If you don't have shaders enabled, you might see some textures glow in the dark
but on pecon7's imscared server, everything was pitch dark, and I didn't enable shaders.
certain textures
Download any of the white-to-black day cycle edits, start the daycycle, set day speed to 0, and set the delay slider to stay at pitch black, that's how I do it on my server.