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.
Lingerie Bridal Shower Cake My Mama taught cake decorating for years. She always included a bikini cake. It was,of course, like this one only the bride was dressed in a bikini on her honeymoon! She used this cake to show you could cut cakes into shapes instead of spending money on expensive pans! Oh, did the students have fun with this one!