Very impressive image! The two people give a wonderful size-scale. Is the ground on which they are standing on the negative? Then it might be great if one could see a small part of it in the frame.
I have to agree with Heinz and small sliver of ground would make more settling to the eye than having them floating in space. But they do make the photo and give it great perspective.
I think this is extremely effective with the ground cropped out. Gives more of an isolated feeling of the people in front of the falls, and to me emphasizes the sheer enormity and brutal force of these water falls.