What a great layer cake pattern! Simple and really showcases and frames the prints! The possibilities are endless with a large selection of layer cakes and other pre-cuts to choose from at the Fabric Shack at http://www.fabricshack.com/cgi-bin/Store/store.cgi
It looks to JustAbitcrazy like it's mock cathedral window, made by sewing two circles of fabric together right sides together, then turning right sides out through a slit in the white fabric which is located towards the side and then covered up when the circles are sewn together forming 4 half circle "flaps". In this case the colored circle used initially is pieced of four quarter square triangles. I've never seen it done with that circle pieced like that.