These screenshots were all from a Japanese flyer (sourced from The Arcade Flyer Archive).
The rightmost tower isn't open. Either the towers didn't open all at once, or it would just close instead of being destroyed.
Obviously, you don’t fight two Allens here in the game, nor are there two whales, although that does look rather awesome. And maybe it's just the resizing and cropping, but Marco's Heavy Machine Gun bullets look rather thin there, like the monkey bullets from MS4.
From Sunny Side SNK Vol. 9, sourced from @shinobi_island on Twitter; credit goes to Rage Quitter 87 for noticing these changes!
That truck isn't there in the final game, and the prisoner is tied to a pole closer to the left side.
This image shows two merchants to the right of a Camel Slug; in the playable game the merchants are furthest left, followed by a cart and then the Camel Slug.
The Bradley normally moves forward once the wall is destroyed, but here it seems to have stayed put.
The camera is higher than it is in-game, reaching right up to the players' feet and showing more of the background than is normally visible.
The Slugnoid is on the left platform in the final.
