These are taken in Hammer++, however it is close to in-game footage.
ACT 1:::::
Pre-river Street: https://i.imgur.com/P7UqPqp.jpeg
River & Bridge: https://i.imgur.com/97IZSXN.jpeg
Panic Event: https://i.imgur.com/HLYsAFY.jpeg
Checkpoint: https://i.imgur.com/RMqhDkw.jpeg
ACT 2:::::
Entrance: https://i.imgur.com/RYPSqNU.jpeg
Centre of The Sawmill: https://i.imgur.com/8bsN9Xw.jpeg
The Tunnel: https://i.imgur.com/jRjng8d.jpeg

I will return when I finish act 3 and 4. Because I think those will be Epic. I need to figure out if L4D2 can handle more than 5 acts however. Act 1's checkpoint, and the entirety of Act 2 is based on an game. A game that has Power Drills. And Massacre. You could say it is an Power Drill Massacre. (c) Puppet Combo 2015.

(I don't know how to put this, but I want to let the reader know that I referenced PDM only because it's cool, and I think it'd be a killer reference. I do not present the layout of Branden Sawmill as my own, and it will be attributed via pages accordingly that it is the Power Drill Massacre Sawmill.