Hmm the colours are very pleasing. I don't like how you do the shadows there, its very disruptive. Office buildings are like any building, they vary a lot, and it depends when they were built and where they were built and what for. I'd imagine either bricks, concrete with steel frames, plaster with steel frames, or thin chip board walls are all possible candidates. Just think about the nature of the building you are setting your game in. For instance, the office areas in Half-Life are an older part of the facility built in the 50s, and you can tell by the style of everything, lots of brick works and old pale colours.
Modern buildings are concrete and steel frame, so if you are going for a modern one thats what I'd suggest.


Edited by EyeCraft