This could be debated. But it would like to be proposed that when you ask or commission someone, an artist, a photographer, a painter, to produce your portrait, you are not acting out of vanity. For purely moral and commercial reasons, you are endeavoring to create something direct about yourself for posterity reasons. You are creating a portrait of yourself for remembering as well. And you will have posthumous portraits of others who are no longer with you.
These may be recently or long departed family members or relatives. Now, how is your portrait artist expected to produce a posthumous work of art? Quite easy actually. It is already a well-oiled practice. All the artist really does is take on photo or a series of photos and recreates something from these in the preferred or chosen medium. And it is left up to the client, that would be you, to choose the medium.
You will more than likely be picking out something truly striking or memorable about your dearly departed and this is how you would want to remember him or her. Striking a pose in real life is never easy. Unless of course, you happen to have that resilient charm or personality. You have charisma. You know how to get on with people around you. But what is wrong with being a little intense at times? Ah, this would be perfect for your portrait artist. What is wrong with being more on the introspective side of life.
This would make a far more interesting portrait surely. Whoever is left to view you on the wall is going to be left wondering just what it is that has left you so deep in thought. It must have been something quite big.