L4DMods.com says it got a look at code detailing what can be expected in the release. Let's let them explain\:

Custom models are now supported and very much a reality now! And that includes survivors, special infected, common infected and weapons. Not only that, it seems the weapon functionality can also be edited. So what does this all mean? Well it means mappers can have custom survivors, special/common infected and entirely new weapons unique to just their campaigns (i.e map side modifications, NOT server side)! The L4D modding scene just got a little more interesting boys and girls.

What does this mean to you, the Left 4 Dead 2 PC player? Well, a whole lot more than just Nude Zoeys, I'd bet. Maybe nude jockey-Zoeys hybrids? It's a start.

L4D2 SDK Content Revealed! Custom Models a Reality [L4DMods via Evil Avatar]

Plus, I mean, god damn, look how long it takes for everyone to get in the safe room.

Here's another video. I love the beginning, everyone running one after the other to the weapons table. As awesome as this looks, I bet it's pure hell to play. We're seeing the reason Valve capped this at four to a side, I think.

This is Why Left 4 Dead 2 is Limited to Four Players [Hot Blooded Gaming]

Enterprising modder samm5506 was digging around in Left 4 Dead 2's code the other day when he stumbled upon a zombie model not found within the game itself. Dropping it into a level, he found it was none other than Mr. Jimmy Gibbs Jr. himself, who aside from being a particularly tough zombie, also brings out a few custom one-liners from the survivors, like Nick's "God damn that Jimmy Gibbs Jr.!".

To drop Gibbs into a game (PC version only, naturally), enable the console, then from the main menu enter these commands:

map atrium
sv_cheats 1
z_forcezombiemodelname common_male_jimmy
z_forcezombiemodel 1

Then have at him. The fact he's dead - and trying to bite your face off - makes stealing his car totally OK.

Hidden Jimmy Gibbs Zombie! :D [L4Dmods.com]

Modder Saul has whipped up a little plugin that allows you to play as the zombies in an online match (PC version only, of course). If you want to host a game, you download the plugin, if you just want to join a game, all you need to do is enter some commands in the console and you're good to go.

Interested? Full details at the link below.

Play as Infected with the Left 4 Dead 2 Demo [L4dmods]

That map, known as "Dismember The Alamo," has just been released for your enjoyment, letting you engage in zombie survival panic, Left 4 Dead style, at one of the world's most revered movie theaters. Creator ZapWizard has offered the Alamo Draft House virtual recreation for download at Left 4 Dead Mods, which seems to be the place for custom maps.

Let me know what you think, since I won't be able to immediately enjoy it. And see if he included the basement.

Dismember The Alamo [Left 4 Dead Mods]

Anyway, "Dead Before Dawn" hits on Oct. 31. The modmakers are working feverishly, and promise that they will put something out on Halloween.

In the event that we do not see our finale up to scratch for release, we will NOT postpone the release. We promised you a halloween release date, a halloween release date is what your going to get. If this does happen, maps 1 - 5 will be released and an update for the campaign containing the finale will be released shortly after.

Further, yes, that is a fifth character in the poster; yes, he is C.J. head of Crossroads Mall security, and yes, he is playable.

You can see tons more screens at the link. It seriously looks like one hell of a great mod.

Dead Before Dawn Community Update #3 [L4DMods via Evil Avatar]

What's more, Mr. Wizard is aiming to have the Alamo Draft House-gone-horribly-wrong playable at said film fest, complete with arcade-style cabinets. The recreation of the famed cinema chain is impressive, with recreations of each theater room in various states of destruction, custom-made posters and stills from zombie flicks projected on each theater's silver screen.

Take a minute to eyeball the work in progress Left 4 Dead map at the forum conversation below, take note of the detail and hope for its swift availability for download following the film fest.

Dismember the Alamo [Austin Modders - thanks, Edward!]

Ryan O'Koren is a student at Towson University in Baltimore, Maryland. He is also a longtime modder of Half-Life games, making maps under the name "mrfanswa". And he's got something pretty cool in store for you. Cold Case is an incredibly ambitious mod for Left 4 Dead that O'Koren intends to complete in time for a Halloween release, celebrated with a big party in Baltimore.

In this mod, over the course of 36 (!) maps, the zombies will dynamically evolve. The players will be able to upgrade their abilities using a lite RPG system. It's got a storyline, complete with new voiceover recordings. There are also survival maps that balance digging in to take a defensive position and running for your life.

But this isn't just a mod. It's part of O'Koren's studies. From the mod's FAQ:

After the release of Left 4 Dead I began gaining interest for an idea which I could not do in previous maps. An entire explorable island featuring such places as a jail, a military base, labs, a dense forest, and an abandoned facility deep within the woods. I decided to devote my sculpture degree to exploring more of the digital arts and I began creating what is now Cold Case. I quickly began development of a small campaign using SDK content, and parts of my old [Half-Life] map [Resident Evil Outbreak 2]. I submitted it to the largest scholarship my art department offered and won! The only stipulation was that at the end of the year I would need to hold an exhibition featuring this campaign, and numerous other sculptures I have been developing over the years.