I propose that top performers are proportionally pleasing photos that have a high-definition focus on the subject and a softer background that does not distract the eye from the central draw of the photo. Photos with an underlying emotional message can help gain engagement, but it is not severely important if the aesthetics of the photo itself comforts the eye.  It is important, however, that the photo has people in it; this allows viewers to  identify with you and what you are doing in the photo.  With people, viewers are also more inclined to leave a comment. Because we are naturally interested to understand what we see, including a caption that supplements the visual image can bring the photo to the next level.  In my three edited photos, I strive to emphasize the Golden Mean, include captions, and  enhance color balance.