I would focus on one small area and fully do the diffuse, spec, gloss, and normals from start to finish. Right now it seems like you have a good hold on the design of the level, but are spreading yourself thin on the art by doing a very little bit of everything. Depending on the art style you are shooting for, the lighting…
The blurry padding is done with the Solidify filter, or something similar. There are a few different ways of getting that effect. MIPs: http://wiki.polycount.com/wiki/Mip_Mapping These articles explain how the UVs and textures are laid out. http://wiki.polycount.com/wiki/Modular_environments
Start from the flat plane with your tiling texture on it, and start to model the cracks and holes to match the texture features. For example: http://www.philipk.net/tutorials/modular_rocks/modular_rocks.html http://wiki.polycount.com/ModelingRubbleIntoAPath
This is a great start! I think the wood needs a bit of modeled detail. The wood timbers on real houses generally sticks out some from the brick. So your model would be better if it has this raised detail. This page on the wiki might help you. http://wiki.polycount.com/wiki/ModularMountAndBlade
It's the same, but they do not depend on BSP alone. For example, you might make a corridor out of BSP brushes, but then you'd cover the flat walls with meshes. That way, you can have the benefits of a BSP tree with the beauty of your static models…
Thanks for the advice man, after looking through some fairly creepy sites, I managed to find this set of images for an underground tunnel that I thought looked pretty cool, and actually fairly simple to accomplish, but i can add enough to make it look cool. Uploaded with ImageShack.us so yeah, not my only ref but just…
You could probably do with baking some AO to the vertices and also add a few decals, also the stones and wood still look quite noisy. Hope this helps - http://wiki.polycount.com/ModularMountAndBlade