Well for marketing purposes, DC Comics did not give enough preview pages of Batman #13. Boo, DC Comics you suck! However, Dark Knight News has been collecting Greg Capullo’s (artist of Batman) sketches of Batman #13 just for this reason.
Warning: some sketches found may or may not be for Issue #13. Due to Capullo’s ambiguous tweeting, he might have leaked different sketches for different issues.
The images below feature Comm. James Gordon and Harvey Bullock smoking in the rain. The two have quite a noir look about them. Whatever, they’re talking about must be about the Joker or some random that relates to the Joker.