The first marks a child makes are really a recording of motion in the womb. The lines run back and forth, either horizontal or vertical, reminiscent of the rocking in the womb. Children under two years old are not making drawings of anything in their environment. They should be encouraged to use markers and crayons on large sheets of paper, with a freedom of motion. When finished, they should not be permitted to carry the markers or crayons away from the “work space”. You don’t need to have your walls redecorated! The more the child draws, the faster each goes through the various stages of scribbling. Let them experiment and express themselves on paper; do not show them “how to” draw anything. They are in a creative space at this age; any attempt at realism is useless, or perhaps, damaging to their self confidence.
See “Understanding Preschool Art”, by Dr. jacqueline M. Shuler, a colorful textbook for parents, teachers, and grandparents to focus on the meaning and progress of children’s art. Available on https://www.etsy.com/listing/228528892/understanding-preschool-art