This is a good 'how to' on a lingerie cake, uses box mix. I would stick with simpler icing design though. You could use those pearl looking sprinkles to decorate with! Or roll out the pre-made fondant if you're feeling really adventurous.
Undergarments of -- tulle petticoats were very popular under skirts and dresses in order to give a crinoline-type appearance, elastic corsets / girdles were used to create a smooth shape and a narrow waist, bullet bras are introduced