Dishonored 2 has 27 Collectible Paintings. Finding all Painting Locations unlocks the "Art Collector" Trophy & Achievement.

The Paintings are scattered across the 9 main missions. At the end of every mission you can see how many you've found. Always double check that you got all of them before proceeding.
All of these collectibles are missable because there is no mission select! You are advised to make a manual save at the start of every mission. In case you missed one you can reload that save and replay from there. Without a backup you'd have to restart the entire story if you miss one.
Everything can be reached as either Corvo or Emily. It doesn't matter what character you choose. When playing as Corvo you should upgrade the Blink range as soon as possible to reach certain places.

The collectible progress is only saved when you trigger an auto-save or manual save. If you die without saving you have to pick them up again. It's best to save after every collectible.
The Paintings also give you 200 coins each which counts towards the trophy "Well Funded" (get 18,000 money in one playthrough). The 27 paintings give you 5400 coins in total.

Each mission features an open world design. This means you can free roam as you like and reach any place at any time, but only if you don't finish the mission. Once you leave the mission you cannot go back. This also makes it easy to work on multiple collectible types at once (for trophies you need all Decorative Objects, All Paintings, All Journals and Audiographs on the Dreadful Wale). For example: go after the one Decorative Object and then collect the Paintings. The other collectibles are on the Dreadful Wale in between missions.

TIMELINE:

#1 - Mission 1 - 0:05
#2 - Mission 1 - 0:23
#3 - Mission 2 - 0:58
#4 - Mission 2 - 1:27
#5 - Mission 2 - 1:45
#6 - Mission 2 - 2:08
#7 - Mission 3 - 2:38
#8 - Mission 3 - 3:00
#9 - Mission 3 - 3:28
#10 - Mission 4 - 3:46
#11 - Mission 4 - 4:11
#12 - Mission 4 - 4:44
#13 - Mission 4 - 5:11
#14 - Mission 4 - 5:36
#15 - Mission 4 - 6:07
#16 - Mission 5 - 6:26
#17 - Mission 5 - 7:02
#18 - Mission 5 - 7:38
#19 - Mission 6 - 8:18
#20 - Mission 6 - 9:20
#21 - Mission 6 - 9:29
#22 - Mission 7 - 10:08
#23 - Mission 7 - 11:18
#24 - Mission 8 - 12:36
#25 - Mission 8 - 13:17
#26 - Mission 8 - 14:07
#27 - Mission 9 - 14:23

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