How are wallpapers unlocked?

Question

I'm finally starting to expand my castle from the cramped little crypt I built at the start, but I'm afraid these bare stone walls (while delightfully imposing) are a tad too dreary for my tastes.

I have Hearth and Workshop wallpaper and their variants, and the Haunted Nights from the free DLC, but the wiki lists other non-DLC options like Cordial and Imperial wallpapers, which, importantly, have color.

How or when do those variants unlock?

(Current progress, if it matters: I'm playing with friends, so I've unlocked iron/visited Dunley Farms but need to backtrack in the quests to do the initial servant/Dominate tasks. I'm playing the current release version.)

Answer 1

Like other decorative elements, some of the wallpapers and wall panels are unlocked by finding the books that contain their respective knowledge, others through the quest progression (do this, click 'Claim', get a reward).

For example, the Cordial wall panels are unlocked through the Study structure.
The Imperious wall panels are unlocked through constructing and interacting with The Eye of Twilight.