Well, when it comes to cartoon muscles flexing, you'll notice that they often have a sort of exaggerated size and definition. It's a way to visually convey superhuman strength or a show of might. Also, the shading and highlighting are used to give a 3D effect and make them look more impressive.
In a cartoon of a strong man flexing, you'd likely see a defined body with bulging muscles, maybe a fierce look in his eyes to show his power. The background could be simple to focus on the man, or there might be some symbols of strength around him like weights or trophies.
Another alternative could be college bodybuilding or strength training success stories. These can be about students who start from a relatively unfit state and transform themselves into healthy, strong individuals through proper diet and exercise. They can inspire others to take care of their bodies in a non - sexual way.
Toge Inumaki is important too. His special cursed speech ability makes him stand out. Also, the principal of the school, Masamichi Yaga, is likely to be important as he is in a position of authority and has an influence on Gojo and the other students. There could be other characters like the members of different clans that also play roles in the complex web of the story.