Listen, we all love Left 4 Dead around here. Love it. You and I are both a little concerned about its staying power, though. The four included scenarios are great, but--let me stress--there's only four of 'em. The game is ripe for future downloadable scenarios, of course, and I'm sure Valve is already cracking on some, but what will be the manner of their release? Will Valve neglect the 360 version and simply put them out for free on the PC, as they've done with Team Fortress 2? Will they appear on Marketplace with a fee? You have to figure someone is going to come out of future L4D DLC (L4DLC?) releases a little unhappy, unless Valve and Microsoft can come up with an equitable solution that benefits players on both platforms.
Anyway. In the short term, there's another, underground, seedier way to get new Left 4 Dead maps: the mod community. You can envision all kinds of nifty themed L4D scenarios coming out of modders' collective creativity. Like, say, a shopping mall. That seems like the kind of place zombies would like to hang out, right? Maybe hit the Hot Topic, grab a Cinnabon?
Someone's already got you covered on that front. The original, the greatest of all zombie shopping malls, the Crossroads Mall from Dawn of the Dead, is forthcoming in Left 4 Dead format. Here's a work-in-progress video of it (sans undead).
This map was already in existence as a part of the Half-Life 2 mod No More Room in Hell, which is a cooperative us-against-neverending-hordes-of-zombies game from back before Valve figured out how to turn that idea into a commercial prospect. Author Darth_Brush is porting the Crossroads Mall map to Left 4 Dead, and l4dmods.com says it will be exclusively hosting the map once it's ready for consumption. The site also promises a "special little surprise...real soon now" pertaining to the map. So check back there real soon now!
I hope this is the beginning of a long and fruitful era of Left 4 Dead mod support. Love love love the game's concept; want more maps, like, yesterday. While you wait, check out some shots of the Crossroads map after the jump. I'm just kidding, we have no jump.