While I've not yet built any Steampunk MOCs, I plan to - it's such a rich "world" with so much flexibility yet features a highly distinct aesthetic. Victorian era sensibilities mixed with modern or even futuristic technology that runs on steam power - how could that NOT be cool?
For some inspiration or, for the uninitiated, for an idea of what Steampunk is, here are some prime examples:

Dampf-Renner by captainsmog, on Flickr

The Chair of Ultimate Power by 2 Much Caffeine, on Flickr

Aether traveler by captainsmog, on Flickr
In terms of minifigure pieces that seem to fit well in this aesthetic, two official themes come to mind: Harry Potter and Pirates of the Caribbean. A lot of the torso prints in both have a certain old-world flair to them. Those that spring to mind from HP are:
Gilderoy Lockhart

Argus Filch

Professor Flitwick

Fred/George Weasley

Two heads that, to me, give off that Steampunk vibe are
Professor Hooch

Luna Lovegood

Luna's spectrespecs especially have that Jules Verne quality to them.
Minifigure images from Brickset. See all the images in the Harry Potter Minifigure Gallery.






