Have you seen this Postcards from Puffin collection? I somehow missed it (although I had seen Postcards from Penguin at Anthropologie) when it came out in the fall of 2010. This would be such a sweet way to decorate a wall in a nursery or child's room.
Here is the official blurb:
A unique collection of 100 postcards, each featuring a different and iconic Puffin book cover. From picture books to paperbacks, teen fiction to Puffin Classics, this is a selection from seventy years of outstanding British design and illustration in one sturdy little box.
I went looking over at Amazon UK to see what else I haven't noticed, and I found a similar collection called Postcards from Ladybird.
When I was little and lived in Australia, we had Ladybird books. :)