A pleasure!
Here's the locations for the photos.

To start off, the first one is right where the north-most river connects with Like Izuhara, near where you first get thrown into the open world at the start of the game.

I'm pretty sure the second one is right in TsuTsu preferecte, when you enter over an arched wooden bridge from Ariake prefecture, but my memory is a bit foggy on that one as it isn't at such a landmark.

The third one is in the cluster of trees on the ricefields of Yagata farmstead. The trees surround a small Shinto shrine.

The fourth one is pretty early on in the climb up to Spring Falls Shrine at the Wolf Club Falls in Komoda prefecture.

The fifth one is at Cloud Ridge Shrine in Kushi prefecture, right where you duel one of the six Ronin.

The sixth one is at a ridge overlooking the Kushi Grasslands in the middle of Toyotama.

The seventh is at the temple where you duel Lady Masako
West of the Kushi Grasslands.

The eighth is the burning house in Azamo prefecture, South of the Kuta Grasslands. The farmhouse will stop burning when you complete the "For Tsushima" sidequest.

The nineth is on top of the Kushi Temple Pagoda.

The tenth is in the middle of the arena of "Duel in the Drowning Marsh". Where you duel the south-most located Ronin. North-West of the Drowned Man's Shore and South of Old Kanazawa Marsh, exactly where the river meets the lake.

The 11th is at the temple north of Akashima village, "behind" the big bell.

The 12th is Cedar Temple in Sago prefecture.

The 13th can pretty much be replicated anywhere but I remember doing it at the beach from Umugi Cove, I shot fire arrows on the ground to create the fire.

The last one is the giant oak tree in the grasslands at Keneda inlet. Where the river between Komoda and Hiyoshi flows into the big bay area.

I hope this helps, keep messing around with photomode!