Specifically I am looking for a resource for "under the stairs". Usually when stairways are put into homes, the space under the staircase is either used as an additional staircase going downwards, or it is left open or used as a closet. I'd like to have that kind of quality in a mod I am working on, and I'm hoping desperately someone has made an in_c block for it.

Suggestions?

Hmm, check out http://www.gamesas.com/index.php?/topic/1103752-cart-resource/page__view__findpost__p__16150375 with Barabus Imperial Housing mod. He made some pretty cool statics for 19th century architecture. You may find something in there.