Sometimes illustrations are the most memorable part of a book and should be considered art all on their own. Instead of defacing our favorite books, we were happy to find many illustrations from children's books are available from Art.com
Above is Peter of the classic The Snowy Day by Ezra Jack Keats ($20 or $40 depending on size).
In the Night Kitchen by Maurice Sendak ($20).
Elmer and the Lost Teddy by David McKee ($9 or $18 depending on size).