Between 1948 and 1966, early education and development researcher Rhoda Kellogg and the Golden Gate Kindergarten Association of San Francisco compiled an archive of over one million drawings by children aged 2-8. In 1967, she published a reference collection of around 8,000 drawings by kids 2-3.5yo, which was used to conduct pioneering formalist analysis of developmental milestones. Kellogg linked the scribble-to-pictorial progression to various Gestalts. It's searchable online, which is a helluvalot more convenient surfing through 300 microfiche cards.
Personally, I'd buy the Bernd & Hilla Becher-style coffee table book version, if it ever came out. Having a hard copy of every possible type of childhood drawing would get me off the hook for throwing out so much of our own kid's production over the years.