At the end of this year, I recreate my just-for-fun research that I also did in the late last year. From my 108 Instagram posts (image only), my data showed me that the post with natural faces got more likes. In the other hand, the posts that contained merely about ideas (meaning not containing natural faces) got fewer likes (see the graphic below).
Disclaimer: this research is naive to the hour of my post, the increase of my followers, the number of likes I gave to the other accounts near the posting time, image quality, caption length, language, tag, location, topic salience, etc. Also, if the posts contained more than one images, only the first images were counted.
This research doesn't related to the institution where I work. The cover pictures in this site are from sources that declare the picture as are free to use.*Disclaimer: the cover pictures in this site are from sources that declare the picture as are free to use.