It is known from an interview and various magazines that yoshi's iland had in fact received a huge graphic overhall due to donkey kongs graphics being rendered, however im wondering were any screen shots shown of the orignal version that was alot less graphicaly impressive.
I dunno if this helps at all, but here were pictures from magazines I scanned a while back of early pictures of the game, in this thread: http://assemblergames.com/forums/showthread.php?t=6442
the copter area looks like its at an early stage. I must admit though its probably extremely tough to find any shots of the first version, still thanks for the scan.
http://www.themushroomkingdom.net/lostbytes.shtml No actual early screens, but some details on a few unused sprites-namely yoshi as a plane, tree and mushroom
