Helping users create characters & stories using AI sounds really interesting. All the best!!
P.S. Almost every highest-upvoted product on ProductHunt has a video along with the screenshot slides.
I sincerely advise you to create a simple Animated Explainer video by yourself if you have the time and expertise or outsource it to a professional. An intriguing video can do wonders to your promotions, it's been proven again and again.