A while ago I experimented with photo-engraving (not with the Vectric software) but my results were not that good, your's are much better.

But I did get some nice results with "edge detect" photoshopping an image (actually using GIMP) , then normal v-carving after some vector cleanup. You do need a good original photo for that where the object of interest really stands out. It would probably not be good method for portraits either. I did that a long time ago and would have to figure out the image processing again.