I think the one crawling is Pippin and the one lying face down is Merry, because Merry was worse off than Pip at first. I'd love a big print of that picture.
Do you think that tall, green thin tree is Treebeard? If you look at his bark, you can just make out two eyes and a nose and mouth. He looks rather startled, just like the Treebeard in the preview!