Well, the problem is, aside from part of the stairs, there is no contrast in the lighting. No definition -- you can barely even make out the windows. It just looks uniformly dark. Also, if there are no lights indoors, this medium-dark outdoor lighting won't be sufficient. Keep in mind that not everybody's monitor is as bright as yours. When I looked at these screenshots at work, it looked like it would be an eye strain to see other players. Use something like midnight as a comparison. If it's darker than midnight, it's too dark.