Remove calvarium (skull cap) and fill with small items. In the picture shown here, items were also fitted into the eyes, nose, and between the jaws (including an eyeball-shaped superball in one of the eye sockets).
Place skull in the center of a square of tulle. Pull up corners around the top and tie with ribbon.
There are several more photos of this gift in various stages of construction at Lilith's Ofoto Page.
Variation: Instead of using Halloween items, make themed skulls for special guests. To pamper your bridesmaids, fill skull with scented soap, body oils, and bath salts, and top with a shower cap. For a friend with a sweet tooth, festoon the skull with gummi body parts (such as a gummi tongue, gummi eyeballs, etc.) and fill the braincase with other sweet treats.