Here's a dropbox link to my "Level Design Inspiration Folder of Magic" - which is 400mb of images of various organic, inorganic and in-between. Used some of these for TF2 things, some for Black Mesa other stuff for various other whatevers I was working on.
Three shots of the National Mining Museum of Scotland. Which I visited recently, it's a very interesting place and the tour guide I had actually worked there when it was functional, so he was really great at taking us round it. Its red brick which is unlike quite a lot of the buildings around there which are made of red or yellow sandstone.