here are some great shots taken from Decorating Your Child's Room from the Doubleday Home Decorating Program, circa 1971, to inspire you. Vintage Goodness scanned these great shots from a pamphlet she found.
Prominent features of these rooms are lots of avocado, trundle beds, and lots of bright patterns. Accessories seem to range from more typical vintage letters and numbers to the stranger whales, soldiers, and zebra prints!
Vintage Goodness has a few more pics and lots more to inspire your modern vintage over at her blog.