Steampunk

Steampunk is a "term denotes works set in an era or world where steam power is still widely used—usually the 19th century, and often set in Victorian era England—but with prominent elements of either science fiction or fantasy, such as fictional technological inventions like those found in the works of H. G. Wells and Jules Verne, or real technological developments like the computer occurring at an earlier date."

Many fine examples can be found here at Steampunk Workshop. There are plenty of other sites out there that showcase this unique and very cool form of artwork (most with a lot of the same stuff you'll find there. If you're looking for something even more out of the ordinary (and even more geeky), there's always Steampunk Star Wars.