We support GIFs across all image uploads, so you can add a GIF as your form background to achieve an animated look. You can also use the GIPHY Plugin to choose a GIF from their vast collection.
In the form editor, click on Theme (waterdrop icon) → UI Elements → Background.
Select "CHOOSE A FILE" under Background Image.
You can then upload your GIF or select GIPHY to search for a suitable GIF.