So, I spent last night (From the day posted.) making an industrial style staircase to overpass pipes and other structures that can't be moved. I decided to add materials to this one, first by making my own textures, but I ended up using some from NOBIAX @ deviantart.com.
He offers them loosely under a CC-BY lisence, mainly just as free-ware, but I respect his wishes and credit him.
FREE High Quality Game Textures from NOBIAX: NOBIAX @ deviantART.com
Although the poly count is rather high, it is optimised for what it is.
I hope you find a use for it, I separated the floor, pipes, and staircase into vertex groups, so select the stairs and press P, Selection if you need them.
Go visit NOBIAX for free textures and enjoy!