Amazing infographic detailing the various foes Batman has come up against over the years: The Myriad Monikers of Gotham’s Villains
Love these: Gotham Villains by Matthew Miles.
Superb Megatron/Killing Joke art mash!
Andrea Rhodes & Saul Ruiz - Batman Heroes
DC Comics style guide circa 1982: classic Batman villains by Jose Luis Garcia-Lopez.