I followed the method of turning 2D images to 3D http://www.appropedia.org/Converting_2D_images_to_3D_for_printing_using_open_source_softwareImages were found using google image search and the criteria: 'celtic knots' http://upload.wikimedia.org/wikipedia/commons/thumb/0/05/Celtic-knot-basic.svg/800px-Celtic-knot-basic.svg.png http://upload.wikimedia.org/wikipedia/commons/thumb/0/04/TrefoilKnot_01.svg/2000px-TrefoilKnot_01.svg.png