Basic shapes, large?
Or perhaps something that seems cute to the parent, and still functions as a large shape for the child. For example, you could make a big dark-green circle on white background, and add some extra lines to make it a frog, while knowing that the child will only see the big green circle on white background.
We don't really have large enough, detail-less books (in our shop). There's a cute series of books made from cloth, but we don't have it, either (I think I will try to change this), but really, there's nothing quite large enough (or maybe I am just wrong and it's alright? Seems not so.)
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