My mom and I got this idea from a gift that my sister got at her baby shower. It looks like a wedding cake but it's made up of layers of diapers. We rolled each diaper so that the fold was on the outside and then held them together with tiny elastics that we got at the craft store (came in a box of 1000 I think). Then we tied each layer with a string (or ribbon) to hold them in place and also to cover the elastics that held the diapers together. We used a medium sized silver platter that we found at the dollar store for the base.
Once all the layers were done, we stacked them and placed a small stuffed animal on the top - I guess we were thinking of a star on a Christmas tree. Finishing touches included sticking some bath toys, socks and face cloths around the finished product, glued lace to the edge of the base and wrapped it in cellaphane. It was the talk of the shower.