For adding animations, go to "General" --> "Animations" in the Resources palette. In the Components palette, you will see the thumbnails for the startup and shutdown images. You can just copy-paste your animations there, by right-clicking the respective thumbnail. (Select "paste", not "paste image(s) into Theme" in the submenu).
Same goes for the startup and shutdown tones, which you can find in "Sounds" in the Resources palette.