Ravaged Art is a form of collectible art piece that players can pick up during Adventure missions. These pieces are found in random locations on maps and appear as glowing art scrolls on the ground.
The art spawns randomly within designated areas on each map, meaning players won’t always find art in the same spot each time they play a mission.
Collecting Ravaged Art contributes to many achievements, and for completing them you are rewarded with complete paintings that are displayed in your keep.
These rewards are purely collectible, but are a fun opportunity to customize your keep and show off to your teammates.

There is the fastest way to collect Ravaged Art, it's not exactly fair, but it's very reliable.
Just watch this video and run to fulfill your weekly quest :)
https://youtu.be/VuI3vJIwuSQ
In addition, you can collect tomes and grimoires for the same Shillings Quests by slightly changing your route. This video shows the locations where you can find them.
P.S. I adapted this speedrun a bit by Basti, especially for this guide, thanks to him for his work!

You'll have to travel quite a long way to the first Ravaged Art.
At this spot, take the barrel and throw it into the closed passage to continue on your way.

Follow these yellow arrows upwards to the small tower.

The Ravaged Art will be to the right of the door in the corner.

The second Ravaged Art will be located before the final event at the top of the rocks.

The last Ravaged Art will be located already in the final event itself. As soon as we go down the elevator on the left side, go around the rock and follow the yellow arrows to jump to our goal.

For convenience, I will add a video showing the locations of all the Ravaged Art.
First 12:05, Second 16:32, Third 17:45.
(thanks for the timecodes @quercingtime)
https://youtu.be/Vffr7kavafo?si=jI0NfM-PW5Bc9VEH
The first Ravaged Art is not far from the beginning of the map.

The second Ravaged Art is on the wooden shelf at the middle event.

Below the final event there is a spacious room in which lies our last Ravaged Art.


Once we pass the first crashed ship, turn right and follow the yellow arrow up to the top, and inside the cave will lie our first Ravaged Art.

In one of the nooks before the entrance to the tavern there will be a second Ravaged Art.

As soon as we destroy the first Tentacles with the barrel we will be in the square, go a little further on the bridge, turn right and jump down. In a small dark corner will be lying our last Ravaged Art.

For convenience, I will add a video showing the locations of all the Ravaged Art.
First 1:56, Second 14:47, Third 20:09.
(thanks for the timecodes @BastiKuchen)
https://youtu.be/EUIF4voQjpY?si=o5TaxIo74qrMyGju