I COULD be wrong, but you may have posted this in the wrong section. It could probably do better in Showcase; but it is not finished... so I am stumped :o
I won't lie, some of your architecture is heavily unrealistic, such as the scene in the trailer with the stairs around 0:54. The carpet up the top is not supported by anything but the wall, which would actually kill someone if they stepped on it.
Also, that area which seems to be a dungeon or somewhere underneath the main setting (around a minute onwards) is too dark for the lights. If you can do so without causing issues with the surrounding corridors, make some pointlights larger than the area of the light source (torches on the wall) which is darker so there is a better fade effect from the source and brighten up your boxlight (if there isn't, put one in), probably around 0.1, 0.1, 0.15, 1. With that said,
this picture is a little better at that, although I know there are no faded pointlights, the room light is adequate enough for the amount of candles.
You have also made some attention to smaller details, such as putting things on the wall and the billboards coming in from the window (even though they are way too bright) etc. I can also say that I am somewhat interested in the story, but my main concern with the trailer is I cannot understand half the things being spoken because I think the music is too loud, or the voice is too soft.
I can't say that I will play your mod, but I might glance over it sometime sooner or later. Hope it does come out the way you want it though!
Edit: Also with that image I linked you to, there is light bleeding in from the wall, evident by the floor, on the left side. Assuming this is from the same type of candles in that picture, rotate it a little bit. These types of candles give off a directional based light, not a central one. You'll notice it when you rotate it