Easy.

The technique was mural painting and he used either freshly laid or wet lined plaster. he also use water to merge it with the pigment and plaster creating a internal part of the wall

It would. a painted portrait would be an important thing because they are official and take real artists to paint and if it was a painted portrait it would mean that there's seriousness and a desire to work together. portraits are maybe even more so important today because they are not a mainstream thing and are made only when we want to impress someone since they take time and will.sending a picture would not be the same as sending a portrait because a picture is just taken with a camera and there's no soul to it. if a picture is a painted one then it can reaffirm, especially if both states people are in it. if it's just a photograph then there wouldn't be much to it.things today are different because there's photographs everywhere and seeing pictures has lost its meaning since they are so abundant and found everywhere. all newspapers have pictures and just sending the same picture as everyone has would not mean much since it's easily obtainable.  perception of authority has changed over the years because the people trust their governments less and less as years go by. before world war two, governments were trusted and presidents were believed to work for the good of the country. nowadays, everyone is looking out for things that might bring the downfall of governments since it has been shown that governments often do bad things to say in power.