Guess I picked a fine time to write Aztec steampunk… (seriously, though, I’m sticking with it for the moment, because it might not be rigorous science or rigorous history, but it makes me broach lots of interesting subjects. Don’t really read enough Victorian steampunk to comment on the above links, but it certainly makes one think. Giving me lots of story fodder, if nothing else).
French steampunk could also be an interesting different perspective. It seems like (at least in literary tradition) France had a much more intrusive government (secret police, internal spies, etc) in the late XIXth C, compared to England or the US.
Unfortunately, I seem to recall that Sterling and Gibson already made extensive use of the “pneu” in The Difference Engine, so you couldn’t get much mileage out of that.
It would certainly be an awesome time period to mine (I’m a big Arsène Lupin fan, and grew up on books set in La Belle Epoque, as we call it in France). It has spies, secret police, the beginnings of forensic science, a rigid society undergoing big changes…
Pierre Pevel has written “Les Enchantements d’Ambremer”, which is a steampunk set in 19th Century France (http://www.amazon.fr/Enchantements-dAmbremer-Pierre-Pevel/dp/2842281756/ref=sr_1_7?s=books&ie=UTF8&qid=1289729370&sr=1-7 ). It’s got a strong taste of Arsène Lupin and all the Belle Epoque stuff (which I love). But it’s very much a fantasy (it’s got unicorns and wizards).
I wouldn’t be surprised if a French writer has done something more SF, but I admit to a strong ignorance in this regard (don’t read much in French).
I read the Difference Engines, but I confess I don’t recall the “pneu” so much…