Death's peak involves many instances of Sprite A being hidden behind Sprite B until Sprite A is required in-game. Here, we can see the three Macabre monsters hidden behind the background.

Just after the part where you have to cross the icy ridge without falling off we can peel away the floor and see a square sprite that looks like a "Footprints in the snow" pattern. In the picture, it's just left of Ayla. Maybe it's just me being unobservant, but I don't remember seeing this pattern anywhere else in the game. Perhaps it was put onto the cartridge then never used. Also, you can once again see two Macabres waiting to spring out.

On the next screen we can find another two by two square that I don't really recognise. This time it's to the left of Frog. I've kept the snow layer turned on in this picture since it makes the rock pattern easier to see.