The office that has the most steampunk vibe is Nick's -- largely due to the mix of industrial salvage and antique wood used by his brother Jordan to make the desk and shelving.
- fabric curtains to soften the industrial edges
- damask wallpapers
- dark colors -- especially grey
- Edison bulbs
- leather furniture
- soft throws
(One of the challenges I'm finding to using a lot of harder materials like metal and stone is keeping it soft enough to be comfortable. Office space perhaps doesn't have to be as comfortable as a home, but I like how they use fabric drapes, upholstered furniture, throws, and wallpapers to soften the feel.)
See more pictures and read more about it at Apartment Therapy and the Blend Studios website.