Can I create animated themes?
Short answer: Yes, but low quality and with a lot of effort. Long answer: The Switch menus do not have enough memory to handle more than one extra background image. Animated themes would require multiple background images, which would exceed the memory limit and cause crashes. There are some who have done it, but it requires advanced knowledge of Switch theming, results in very low-resolution backgrounds, and is not recommended for most users. View the guide here. Example themes: