Introduction:

Shortly after reading on it will become apparent to the reader (you) that this my Foreign Treasures remake of Left 4 Dead's (the first one) Generator Room.
I know what your first question's gonna be: What the hell is a L4D remake doing in the competitive section rather than casual?
Well, my friend, I have the answer for you. This map was originally built to suit the custom L4D infection variant that is presented later in the thread.
However, with a few tweaks here and there this map turned out to work exceptionally well with other gametypes as well (Slayer mostly), and so that's why it is seen here in (queue French accent) le competitive section. I also saw this as a prime opportunity to get at least one map here since I'm a dominantly Infection oriented forger.
Anyway, useless information out of the way here is:

L4D's Generator Room

L4D Infection

This map follows the original (in survival mode) to the best of my ability.
Certain things were altered slightly for the benefit of playability, but the overall elements of the original are still there.

Pictured above is an overview of the middle and top level of the generator room (ignore lack of weapons right now).
This is where most of the action happens.
Short to mid-range weapons are available all over the map making this stage of the map the most prominent for firefights.

Above is the turret room. In the turret room is the turret (duh), a regenerator, and a transit to the ground floor.
In most gametypes the turret actually isn't there and there is a gravity lift beneath the hole, but more on the differences between symmetrical and asymmetrical games later.

This is from above the turret room.
This just gives a better look at the map from a different angle.
It is here I'd like to take the time to mention the switch I had made to open the door to the upper level.
In L4D it would have been the switch that started the crescendo event.
I was so proud of it, but in the end it had to be removed simply because it caused so much error.
So... sad face =(

It was hard to get a picture of the ground level, but anybody who knows L4D (or not) should know that it is simply a room that is 7 x 5 with columns galore.
In the L4D variant it is also the only place humans can collect weapons, so think twice before hopping up to the top as fast as your l'il feet will carry you.

Now that the reader (you) have seen the meaningful aspects of the map, I'd like to take a moment to discuss the symmetrical versus asymmetrical attributes of the Generator Room.
For the sake of understanding lets compare an asymmetrical gametype (Infection) with a symmetrical gametype (Slayer).

For starters, in Infection the weapons are only on the bottom floor whereas in Slayer things look a little more like...

...this. Now while on the subjects of weapons I'd like to list out the weapons you'll find while playing any symmetrical game compatible with this map:

Guns
Assault Rifle x 2
Battle Rifle x 3
Carbine x 2
Needler x 1
Plasma Rifle x 1
Shotgun x 1
SMG x 2
Spiker x 2

Equipment
Frags x 2
Stickies x 4
Fire bombs x 2
Regen x 1
Trip Mine x 1

With that outta the way lets move on to other differences between Infection and Slayer games.

This is what the corner of the top level looks like during Infection

This is what it looks like during Slayer games.

It is a transition straight from the ground level to the top level.
This helps with map flow creating multiple ways to the top and discouraging camping as such.

This is just below the hole in the turret room.
In Infection the only way through (for humans) is down.

In Slayer, however, this is not the case.

That is about it for asymmetric/symmetric differences though there are other minor ones.

You might be wondering what game modes you can enjoy this map with.
Even if you're not, here they are:

Slayer 2-4 players
Team Slayer 2-4 players
Oddball 4-6 players
Infection 4-8 players
L4D 8 players

Technically it's compatable with 1-flag but there were balancing issues. Some found it fun but others found it stupid.

Explaining the custom L4D variant is pretty easy.
Humans have health and mobility similar to that of in Left 4 Dead.
Zombies on the otherhand spawn in class selection rooms that correspond with boss zombies in L4D:

Active Camo = Hunter (unfortunately)
Sentinel Beam = Smoker
Flare = Boomer
Power Drain = Spitter
Hammer & CP = hmmm... I wonder what.

That's about it as far as everything important.
Here are a couple action shots.
Download links below those.

Download Generator Room

Download L4D Infection Variant

Thanks.

Peace FH.