Before we continue on to my rave review of 'your' map I feel that there is a matter we must clear up first. You see, this isn't your map. If possession were based merely on the ability to throw the shitty alien textures on a map and make it dark as fuck I would have published Paradise Lost. That being said, doing the above you've made an already mediocre map simply terrible. Said map was created for netplay, and I must question your judgment in choosing it to "make" your solo/coop map. If you simply must 'solotexture' (you obviously don't solomap) at least steal a decent singleplayer level. Gameplay is sub par to placing your penis in a blender, turning it to the highest setting and attempting to sing Mozart's Requiem Mass, the lighting is of course completely flat and I can't see your texturing job to judge it. There are forerunners and pioneers for everything and I don't want to discourage you , after all, theft of intellectual property rights may just become the next big thing in Marathon mapmaking, I just think you should alter a different level perhaps more suited to solo play.
Under Veil of Night is a solo map based off of Envy's map "Citadel". I retextured it in visualmode.lua to make it a nighttime version. Don't complain about how you can't see where you're going at times, because that's the point. There are certain bright points for reference.