Also, they aren't easy to find. At all to be honest.
Below are the Serpent Emblem locations for Leon's campaign.
#1 - After you meet Liz's father you'll want to head left towards the computer table. Don't go through the exit door. It's in an open storage closet near the computer.
#2 - You'll escape a horde of enemies and then proceed through three offices. Your goal here is to find a keycard. Instead, notice the three desks next to one another in the third office. The emblem is in the drawers here.
#3 - After the lights go out go through the door towards the train tracks. Drop down here and head right to find the emblem under the train.
#4 - After Helena gets thrown over to open the door you'll be in a bar of sorts. Head straight past the counter and then you'll want to turn left. The emblem can be found on top of the counter near two barstools, under the bulletin board.
#1 - The chapter will open with you near a cemetery. You'll want to follow the path that winds through it until you see an arrow on a green sign. This is right next to a very tall lamppost, near a giant alder tree. Face the green sign so that the arrow points to the left and you should see the emblem on the backside of a tombstone.
#2 - Immediately after entering the Cathedral you'll want to run straight to the altar. Once here, turn around and aim high between the two small pillars towards the massive entrance window. The emblem can be seen up here.
#3 - Once you get to the interrogation room (underground) you'll want to continue forward until you find the men's restroom. It's on the left side of the hallway. The sink needs to be drained to find the emblem.
#4 - Slide down into the shallow water and crawl through two archways. After the second one look to the left and you'll see it on top of some beams.
#1 - Before you even open the door in the beginning of this chapter look up and left. You really can't miss this one, it's in the first room you encounter.
#2 - This emblem is found inside a coffin after you see the water serpent. the coffin is on the left side of the dry path.
#3 - Note: this is different if you are Leon or Helena. As Leon, you can find this emblem easily by simply looking to the right as you are covering Helena.
If you are Helena, turn around before lowering the bridge to find the emblem just chillin' in front of you.
#4 - Note: this is different if you are Leon or Helena. As Leon, climb out of the water after Helena is covering for you. Do not go through the metal gate, but instead turn right and go up the ladder. This is where it gets a little tricky, so follow me closely. Once up here you need to backtrack quite a ways. You'll find some old broken barrels with the emblem inside of them. If you find some 5.56mm NATO Ammo then you're in the right spot.
As Helena you'll simply find this on your trek. Honestly can't be missed, they basically throw it at you.
#1 - This one is found behind the stairs and to the left. As soon as you head down them turn right. You'll see the emblem back there.
#2 - Go to the back of the plane and notice the glass cases with all the liquor. It's in there, fairly visible.
#3 - This one is easily found by heading down the alley to your right after the cutscene with Hunnigan. There's a store to the right of this alley that has the emblem in its window.
#4 - Just before you throw Helena across the rooftop gap, aim up and to the right. The emblem is up there, just waiting to be loved.
#1 - This one is in the clothing store on some shelves to your right. If you miss this then I'm sorry but you should probably put the controller down.
#2 - Look for the soldier zombie near the empty Humvee shortly after the whole scene with the helicopter that's on fire (get to the Choppa!). Once you see this Humvee simply head left and you'll see it in the back of a truck.
#3 - Do not go through the double doors leading you away from this area. Instead, look to the right and you'll see the emblem on a shelf. There's a very long yellowish rail that will be your guide. It's over this to the right.
#4 - Head up until the boss fight here and look behind the stairs. The stairs I am referring to are located after entering the large metal door.
Header image source: vgfaq