the painting was painted by irl Verso as a child and a fragment of his soul maintains it, he painted the gestals (based off dogs) and Esquie, and him and Clea and Maelle used to play in the world as kids. after he is killed by the Writers Aline-mom dives into the painting to live there in her grief, creating Painted Verso and Painted Renoir and Painted Alicia and the people of Lumiere in a facsimile of Paris to while away her grief.
this is chill for a min until irl Renoir crashes into the painting and Fractures the world, trying to expel Aline from the painting and destroy it / everything / everyone in it so she can't return and drug cope anymore. they are fighting for decades and Renoir creates the nevrons, with an assist from sister Clea, to capture all the chroma of which the painting is composed. Aline tries desperately to maintain the painting but cannot, and the countdown is Aline warning the citizens of Lumiere of Renoir destroying more and more of the painting/chroma each year.
Painted Verso goes against his painted family to get his mother-creator out of the painting, and later because his existence is misery and he simply wants to die / free the soul fragment of irl Verso / not see irl Alicia consumed by the painting. Maelle-Alicia wants refuge in it because her waking life is pain and disability and alienation and the painted people she's lived with are as real and important to her as any. the writer has said many time there is no good or bad ending it's all French and sad.