Painting can be an object that can only be placed attached to wall.
I don't think painting is very dwarfy, my personal idea is to have different races have different art. Dwarves engrave, humans should make paintings and tapestry and sell you, elves should probably make bonsai trees and also bring them to sell. Trees that are grown into shapes like statues.
This is a grown mango wood figurine of a dwarf. The dwarf is striking a menacing pose.Now we just need paintings and tapestry for humans, even though we have something like tapestry.
This is a hemp fiber figurine of a dwarf. The dwarf is striking a menacing pose.One could interpret this as a plushie toy or a tapestry, and cloth decorations with depictions of objects could count.
This is a troll fir sock. On the item is a well crafted depiction of a dwarf in hemp fiber.Although, the player should have an option to allow paintings, even if it's "undwarvenly." Player freedom is important.
Another option is letting human immigrants with "painter" skill do it.