From Ellis's explanatory text:
Immerse yourself in the era of Steampunk, and the coal-fired industrial nightmare of Gotham, where is set the popular silent films concerning The Batman. Or even The Bat-Man, if you prefer.
Your task is to design a poster, suitable for placement outside a cinematheque or other theatre, regarding one of these films. There are several in the series I have not mentioned, and you are of course free to make those up. I mean, use them wisely.
The creation above, by Michael Nelsen, is but one of the many steampunk movie posters assembled.
Here's a handful more of our favorites from the challenge. See them all (and MUCH more) in full-size at the above Steampunk Batman link:
The Batman Meets Der Golem by Ken Miller
The Surprisingly Rapid Descent of That Most Magnificent Bat-Like Gentleman! by Geof Banyard
The Batman—Battlefield Mannequin: Road To Mafeking by Neil Ford