There's a Watchtower illustration from the 1950s of the serpent as a sort of lizard.
The 1953 book titled, "New Heavens and a new earth" shows a lizard talking to Eve on page 81 in the chapter named, Corrupting of the righteous world. The creature is in the tree and is about 2 ft tall when sitting on its hind legs. The tail extends about 3 ft from its pelvis and wraps around the trunk of the tree. The lizard sits a little higher than eye level with Eve, I know all would rather see a scan of the picture but I don't want to ruin the book by forcing it open face for my scanner. I just bought it a few months ago on ebay.
In that same picture the image of Eve is rather risque showing her bare butt and side breast. I guess since it's a cartoon they had no problem with it. Another thing to note about this book is the Stegosaurus hanging out with a woolly mammoth and a couple of saber tooth tigers on page 60.