So long as you label the book correctly, and sell it in the proper categories (i.e. don't label it or market in a way that pitches it to children), and it doesn't includes sexual images of children below legal age, there shouldn't be any problem with non-sexual images of nudity.
Any images of nude children are likely to arouse some negative sentiment from certain people (even the once-iconic "baby in the bath" photos are now often demonized), so you may want to get an opinion from a lawyer before publishing, to ensure you're clear of (legally defined) child pornography. You may also want to choose carefully the market you offer to -- for similar reasons.