I think the look of Steampunk is likely the first thing to draw a person in. Unlike fantasy or mystery or romance, the aesthetic of the Steampunk genre is a defining characteristic that, though open to interpretation, is pretty firmly rooted in some general concepts. Victorian era clothing, steam- and coal-powered technology, goggles, bustles, faded leather work gear, bowler hats and spats: these are all things that come to mind when I think of Steampunk. Granted, offworld Steampunk is likely to take considerable license with the imagery, but there’s still a pretty good chance for a corset to show up.
The illustrators of the genre have put out some really impressive pieces. This particular piece by PReilly is one of my favorites and, considering his collection, it was hard to pick just one. The brass and copper, almost sepia, tones of the image lend an air of history to it that transplants it firmly into a time since passed before you even note the top hats, walking canes, and the fine hat and bustle on the woman in the bottom left. The tremendous automaton, reminiscent of The Iron Giant, looks harmless and functional – just how I like my giant, mindless automatons.
http://www.deviantart.com/ is solid place to go image hunting for more Steampunk art and, really, almost any sort of art you’re looking for from yiffing furries to Bob Ross tribute landscapes. The search feature is pretty solid. Use it or ignore it as you see fit. It isn’t always safe for work, but you could probably get a few good searches in before something you shouldn’t be looking at in a grade school computer lab pops up.
The costumes people put together for conventions or gatherings or whatever other reason they’re using as an excuse to go about dressed as a dirigible pilot are quite impressive. This fellow is VladislausDantes, another deviantart member. The goggles on the top hat are pretty characteristic of the Steampunk aesthetic, but that’s just the tip of the coal-driven, clockwork iceberg. A brass breastplate, artificial and articulated robotic limb, and what may or may not be shoulder mounted flamethrowers. A must have for any Victorian-era gentleman.
(I have a friend who has recently started piecing together his own Steampunk-inspired weaponry for fun and I don’t doubt that he’ll soon be tailoring waistcoats and knickers.)
Whatever the reason that people have found themselves interested in or inspired by the genre, I think that the look and feel of Steampunk is more important to its essence than would be true of any other genre. Fantasy and Science Fiction can develop the same sort of fan base, but it tends to be specific to a single author or his/her environment. Lord of the Rings junkies and Trekkies are certainly out there, but they exist as tribute to one world and one created reality. Because the imagery of Steampunk is so prevalent, the art and costume inspired by it more easily spans a multitude of Steampunk environments. Eventually, I will make my way to one of the many Steampunk conventions. Once I’ve crossed that threshold, I fully expect the first bowler hat to appear in my closet.