Paintings also get a "Death bump" of §930 and then appreciate at double the rate. Having non immortals do it can be a museum bump but for convenience it's easier to have immortals do it.
Painting is off topic but here's a blurb: For level 5+ only: Skill level of the painter (at the time the painting was created) is multiplied by 0.5, 0.75, or 1.0 (depending on canvas size) and that value is added to the painting every other day for the remainder of the painting's existence. For example, if your Sim is skill level eight and they paint something medium, 8x0.75=6 so six Simoleans will be added to the value of the painting every other day.
Sculptures have a flat 2% rate until after death which is 4%.