When I looked through the initial submissions, my first inclination was to choose images that had high aesthetic values. Next, I evaluated how much the image related to the assignment and illustrated the concept of the equinox. The best pictures hit that sweet spot of combining both attributes into a single image.
There was certain subject matter that many contributors favored for this assignment. Certainly flowers, birds, and sunsets are a part of the arrival of spring and the day of the equinox. If you choose one of these subjects, you must try to do them in a unique way, as they are so often photographed in a straightforward manner. Unusual angles, compositions, or lighting help, but thinking of new ideas or situations is probably the best way to stand out in a crowded field. On a technical level, many submitted photographs taken with high ISO could have benefited from noise reduction. Many also lacked shadow detail and toning that could have enhanced the mood and presentation of the finished image.