Unfortunately, my only knowledge of top ten children books list is a list of the ten
worst children books out there, made by Cracked. And they are not even free!
10 great children's books for people who hate their children.
On the plus side, the Internet Archive has some illustrated children books, including the Alice in Wonderland series and some old fairy tales. They are old enough to be in the public domain. But they may be too hard for toddlers unless you are planning on reading them out loud to them...
http://www.archive.org/details/alicesadventures00carr
http://www.archive.org/details/tures...dven00carrrich
http://www.archive.org/details/throughlookinggl00carr2
http://www.archive.org/details/grimmshouseholdt00grim
http://www.archive.org/details/fairytales00hauf
http://www.archive.org/details/fairytales00ande