I can never find out all the details on cutting a lithophane and getting result that are posted on the forum.
Joe, that's basically because there are to many variables that come into play, the only real way for you to get repeatable good results is to do your own experimenting & work out what works best on your machine using your tooling
Take the type of tool, speed & feed info from other peoples posts & use this as your starting point to fine tune your own machine. It is also worth noting that the photograph you use will make a big difference as well. Most people will do some photo editing before they import the picture to toolpath.
The material is probably Corian but that is just a trade name, Corian is a solid surface material & there are a lot of other brands that you can use. Try a search for solid surface material & you will get a lot of other names for materials that will work for this sort of thing.