The best thing about kid art, especially early kid art, is how wild and abstract and free it can be. The thought of making it look like something or the adult comment "I can't draw" never even enters their mind. Instead it's really about the experience and how it feels to drag the crayon across the paper (or the bathtub wall in this case). I think there's some pure pleasure in use of material that we could learn from here. Just an open ended experimentation with materials, with color, with line. Creating just because you feel like it.