Ok, so you know that warning of some beatmaps that say "This map has rapidly flashing colors" and the background has moving/animated images? How do I add animated images in the background for my beatmap? If you can help me, Thank you!
What you are looking for is called storyboarding. If you want to learn Storyboarding, checkout the subforum dedicated to storyboarding and the documentation in the wiki. If you use Discord you may also want to join this server dedicated to storyboarding.