Walter Simonson has been posting lots of pirate art lately on the Official Walter Simonson Page at Facebook. In one post, he describes the project as "one story in a set of stories I'm working on for a single project. So, basically, it's a one-off of a character I drew in another one-off 30 years ago." One reader guesses that's a reference to Captain Fear, an early-'70s DC character from Adventure Comics whom Simonson drew some back-up stories about for Unknown Soldier in 1981.
Rich Johnston concurs and offers an old quote from Simonson referring to the Golden Age stories as "beautifully drawn," but "an historical rat’s nest" with ships, uniforms, and weapons from many different time-periods (or no recognizable time-period at all) appearing in the 1850s.
Captain Fear later appeared in John Ostrander and Tom Mandrake's Spectre series in the '90s as well as Brian Azzarello and Cliff Chiang's Doctor 13 story in Tales of the Unexpected. Most recently he's shown up in last year's The Outsiders #26 and Peter Tomasi and Gene Ha's story from Superman/Batman #75. There's no telling exactly what Simonson's working on, but I'd love to hear guesses in the comments.