Ooh, that pic from Roomy reminds me of Doom, and that last shot from your unnamed map reminds me of a section in Halo 1. It all looks good.
Suggestions. TL;DR, I think.
Oh, and Knowitall, perhaps, rather than give the humans no chance whatsoever to respawn, why don't you lock the reactor in a hidden room, and place repeaters every so often, hidden in the walls (next to a medistation, or something, so they don't explode). Perhaps you could nobuild large sections of the map, so that humans, if they ever hit S2, can't build repeaters everywhere. This way, humans aren't doomed to empty their clips within the first five minutes. Start them off with a few nodes, and force them to build an armory. If destructible entities ever get released, perhaps it'd be possible to have a system where humans have to open a blast door, and then aliens can blow up barrels or something to close off passages, or prevent the humans from reaching the escape craft at all?)