Which of these four images is the result to the above and why?
I, too think it's the Mona Lisa:
Both the shape of the Nautilus Pompilius and distance/pattern of strawberry seeds are examples of the golden ratio, as is the Mona Lisa(and other Da Vinci Paintings AFAIK) (Partial credit to lois6b). The letter puzzle could be considered a code. I think the riddle refers to "The Da Vinci Code".