Also, they aren't easy to find. At all to be honest.
Below are the Serpent Emblem locations for Chris' campaign.
#1 - You'll eventually reach a room with two pigs hanging (yum, bacon). The emblem is located on a shelf behind them.
#2 - After the J'avo fight and the proceeding wave on enemies coming from the garage, head into the next room. Keep heading straight into a crate that can be smashed, revealing this Serpent Emblem.
#3 - Turn around after the "Ace of Spades" cutscene and look for a building covered in a green fabric. It's off in the distance so make sure to aim to see the emblem on top of said building.
#4 - DO NOT USE THE ELEVATOR DOWN TO THE FIRST FLOOR. Head up the 6th floor during the whole hostage part of this chapter. You'll find it by some hanging meat (again). Sorry for yelling up there...
#1 - During the scene where you have to cover Finn, screw it and run backwards. Once you are at the other end of this room, you should notice the emblem through some bars. It's to the left of some stacked rubble.
#2 - Note: this will be different if you are Piers or Chris. If you are Piers, this emblem can be found at the point where yourself and Chris split up. Simply head to the spot where you can see the whole bridge and look to the right of it. You'll see the emblem in the distance about three beams from the set of stairs. It's small so zoom in to get the best view.
As Chris you will be able to get this one by dropping down after you blow up the tank on the bridge.
#3 - Go into the mansion and head around the perimeter. You'll eventually end up behind the stairs. Go down the hallway here and you'll see the emblem on the wall to the right.
#4 - Don't go through the door with Ada right away, but instead head into the adjacent room. You'll see the emblem on top of an old rusted door with three windows.
#1 - If you turn left after you get access to the street you'll find this emblem on the right sidewalk (it's up a bit). Look for a blue sign with an arrow pointing diagonally right. The emblem is near this.
#2 - Once you are inside after blowing up that stupid helicopter (I freaking hate these) you'll walk past a dead guy. Keep going through the door and head left. Now pay attention: go through the room with all the gambling stuff and you'll end up in a bedroom. The emblem is on the lower bunk, near the head of it.
#3 - Another helicopter fight scene will place you on the balcony of a tall building. Instead of immediately blowing it up, look up and to the left fairly high. The emblem is up there, on top of some steel beams.
#4 - After you are ambushed by those damned J'avo you'll find the emblem on the bus in the middle of the room. It's behind all the J'avo firing at your behind their vehicles (pussies).
#1 - Head right inside the hangar towards the front of the helicopter. You'll see the emblem in the cockpit.
#2 - Why is that boat shining it's light in my eyes? What the f... oh - there's an emblem there. Thanks Captain!
#3 - Head up the ladder that has been lowered for you until you reach a yellow-railed set of stairs. You should have already seen the emblem behind these stairs. If not, well, it's there. Open your eyes.
#4 - Note: this can only be found if you are playing as Piers - sorry Chris. After you leap from the jet, head forward until you see the emblem behind a tire to the right.
#1 - Crawl through the fan as Chris and shoot the emblem to your right. As Piers, simply shoot it through the grate in the floor. Easy peasy.
#2 - Aim up and right immediately after Chris and Piers open the door together. It's high and to the right in a passageway. If you can't find it, simply look where the enemies keep spawning.
#3 - This one is found on the ground near some crinkled tubing (yes, that's the technical term). When it all seems too quiet you'll find this one.
#4 - You need to really pay attention to get this one. It took me at least a few times to finally get it. When you are going through the barriers it's on the right as you approach the third. Just pay attention to the right wall and fire as many times as you can once you see it.