The rabbits by John Marsden and Shaun Tan. This is a story which represents an allegory of colonisation using images and minimal text.
Gervelie's journey: a refugee diary by Anthony Robinson and Annemarie Young, illustrated by June Allan. This is a non-fiction book with text illustrated by line drawings and photographs. It's part of a series in which the authors wanted to allow children to "put their feet in the shoes" of others.
Boy overboard by Morris Gleitzman. A chapter book consisting entirely of words, this tells the story of two children who journey from Afghanistan to Australia.
Since posting the above, I've come across a blog post by Trevor Cairney at Literacy, families and learning which is relevant to the idea that pictures can help improve literacy. See "How drawing can improve reading comprehension."