On DeviantArt, Genesischant has a great "Jazz Age Justice League" poster complete with back-stories for all the reimagined, Gatsby-era vigilantes. I especially love Wonder Woman as a flapper, and the Green Lantern as a soldier-turned-jazz-musician-turned-crimefighter.
The J.L.A. is a borderline legal bounty-hunter/vigilante group with limited governmental sanction ("Department of Justice Licensed Agency"). Made up of individuals from various walks of life, all are committed to the take-down of the rising criminal empires that threaten America.