Has a proto of this game ever been found or sold? The changes made throughout development are just amazing. It was almost an entirely different game: http://www.rarewarearchives.co.uk/view_guide.php?id=65&gameid=1 Surely someone found one of the builds over the years.
That single screenshot of Dream was from an excellent Banjo article in a magazine a few years ago. It's a pretty large, high quality picture, so it's possible it was taken for that recent article. Makes you wonder where the cart is!! I've browsed Rare forums for years and I've never seen any mention of protos. Of course someone here might know more. I would love to play an early version of Banjo, so I can only hope something pops up someday. Grant Kirkhope has posted some Dream tracks as well as some beta Banjo ones he composed, as well as interesting insight to both. Super cool, and you can hear specific sections of songs that made it into later games, some as recent as Viva Piñata if I remember correctly!