This figure should summarise the contents of the seminar in a concise, pictorial form. It will include the background, methods, results and take-home message(s) of the talk. A short description of the figure should be provided in a capion.
Building this figure, while writing the outline of the essay, will help you to structure the essay and to think about the important messages. If the talk is rather theoreretical or does not present results, the figure will show more the conceptual framework.
If the talk is about a methodology, the figure will detail more with the methodological steps.
It is possible to use and assemble already published material to build part of the figure, providing that the sources are correctly cited, but this should not be the main part of the figure, the main structure should be produced by you. Photos and icons from the web that are free to use are also allowed. Some possible software that can be useful to build the figure: Power Point, Publisher, Illustrator, Biorender or open access Gimp, Inkscape (non-exhaustive list).
The figure has to be sound and clear, but you can earn 2 bonus points for particularly good design.