I think its new stories, but containing some of the same characters and settings.

Anyway, for more on SIN CITY and the other non-filmed tales, check this out:

http://www.moviepoopshoot.com/comics101/109.html

For those that are too lazy to click on the link, here some possible tales that might be told in a SIN CITY sequel:

*A DAME TO KILL FOR - Which introduces Dwight, the protagonist of several SIN CITY stories to come, and details his lethal seduction by the gorgeous but calculating Ava, who manipulates Dwight into killing her rich husband, then shoots him in the face and leaves him for dead. Dwight recovers and plots his revenge thanks to the girls of Old Town, particularly his ex-girlfriend, the tough-as-nails Gail, and the whisper-quiet ninja Miho.

All this comes from the link, and I'm not sure if the film took elements from different tales and combined them, since I really only read THE HARD GOODBYE comic but the others I haven't had a chance to check out.

*FAMILY VALUES - Which brings back Dwight and Miho on the trail of revenge for one of their own, caught in the crossfire between rival mobs.

*TO HELL AND BACK - Where Wallace, an ex-soldier and aspiring artist, stumbles across a beautiful woman trying to kill herself, and is drawn into a deadly mystery when she disappears. The last(so-far) SIN CITY story conjured up by Frank Miller, it also featured one nutty drug-induced acid trip of the protagonist that involves Captain America, Dinosaurs, to Rambo.(check out the web page for the sampling of panels on this). Apparently, according to the Trivia page at IMDB.com, Johnny Depp was supposed to play the part of Wallace in the film version before the segment was scrapped before production due to time and narrative-reasons.

Interestingly, DiCaprio was originally supposed to play "The Yellow Bastard" instead of Nick Stahl. Of course, knowing how many of you hate DiCaprio with a passion, and with all the circumstances that occur with the character, the movie would have made more money probably.

Anyway, Michael Douglas, or Gordon Gecko himself, was originally going to play Senator Rourke. Would have been totally fun, but Powers Boothe is always a totally fun villain-character.