Every other item in the game is pretty clear on it's use (besides the postcard, but I do know what it does), but what does the ancient map scroll do? it clearly doesn't match up with the normal map and it seems unrelated to anything?

The ancient map scroll is a small image which is generated when the world is generated. If i remember correctly from implementing it at he time: the colors of the ancient map scroll also tell something about how the powers ups are distributed through the world.