I found a cool online tool called Zebratrace - 'ZebraTrace is a simple tool to trace bitmap images into a pattern of curves with a variable width. You can control amount of curves, resolution, min and max width, functions for plotting the curves. The application was created primarily for Guilloché pattern design and all kinds of creative engraving.'
I've used a photograph of the Eiffel Tower I snapped during winter when it was covered in snow. I think the results are very interesting. It was a good test for the 3D printer and the process. However I prefer a less photorealistic look. I believe the Guilloché effect is similar to that used to render images in the design of banknotes.