Is there a way to change the photograph of a portal? I know that we can submit new photos for a portal and sometimes I see that portal photos do change but I don't know how they are being changed.
Portal photos do have a "like" button (the thumbs up icon) beneath them. The most liked photo is shown on portals. All players have a vote on photos. You can't dislike a photo but you can take back your former vote by repressing the "like" button. A former vote is represented with the same icon drawn with a yellowish contour.
I don't know the process with two photos having the same count of likes. I guess in that case the oldest one is being shown.