I hope im not the unluckiest guy in earth cause I have tried more than 60 times to set a 4x2 paintings surrounding the place with blocks to make it fill that space and the biggest painting was 2x2.
Even in a 5x5 surface I tried some 30 times more and also the biggest painting was 2x2
I tried in 15w36d and I could place bigger paintings, but not the one i am looking for yet 😞
show a screenshot of the wall, and where you're trying to place it