I realize I forgot one of my favorite books and a must-read for two years old on up until a child can read on their own. The book is Harold and the Purple Crayon written and illustrated by Crockett Johnson. I personally have Harold's Purple Crayon Treasury: five adventures with the purple crayon.
When I was young, my favorite color crayon was red, or so my mother informs me, and I, too, enjoyed expressing myself on the living room wall behind the couch... or so my mother informs me. I actually don't remember this, at least on a conscious level, but something in me resonates with Harold because as an adult I thoroughly enjoy following Harold as his crayon takes him from adventure to adventure.
The illustrations are very simple just a little boy and the pictures he draws on his bedroom wall. His scrawlings always seem to get him into a fix of some sort but are able to resolve, usually with Harold drifting off to sleep.
Anyway, you've got to add Harold to your library.