I also remember being very fond of "Frog and Toad" books. I don't know if those are still around.
One of my favorite picture books from when I was a little bit older was "Rat's Magic." It was a very funky, dark book, but I still have it. The artwork was fantastic. I remember lying on my bed and staring at the pictures, just enthralled.
eta: It's still around. Check out the artwork HERE.