Variations of the finale appear based on your overall item collection percentage (time taken to beat the game doesn't count). See below for the added ending scenes and their requirements.
SPOILER WARNING! Don't read on if you want to see the endings yourself.
Complete the game with less than 75% items collected:
Upon parting ways with the eternally-grateful Luminoth, Samus departs Aether aboard her ship.
Complete the game with between 75% - 99% items collected:
Upon returning to her ship, Samus removes her Power Suit completely, revealing her sporting the blue jumpsuit first featured in Metroid: Zero Mission.
Complete the game with 100% items collected:
After the credits roll you'll discover who the lone survivor is from Dark Aether's utter destruction.