The most memorable visual aid I have seen used was when a psychology professor used graphic descriptions (through historically important paintings) to illustrate abstract concepts, such as love, madness, and despair.
The representations used in the presentation stuck in my mind because of the visual impact that correlated with my personal experiences, making them vivid and memorable in my mind.
The points illustrated aimed at demonstrating the universality of human passions, and as such, it was an extremely successful presentation.
Finally, what I learned from this experience is that human emotions are not only universal, and as such, they can be represented, but, also, and most importantly, they are emotions that are not abstract concepts, rather, singular and personal experiences to which, paradoxically, everyone is subjected.