original Designers of the remix files:
As just a heads up this is my 1st post so you milage may vary. I used https://itslitho.com/ 7cm diameter and 3mm rim top and bottom to make the lithophane the stuff in the site doesn't really change how I was expecting (probably just a me issue) so I would recommend picking your image and then adjusting until you get it to look right, printing the lithophane and then measuring the base and adjusting the top/bottom step file included, what has worked consistently for me, is measuring it and increasing the diameter by .2 which gave me a loose/slightly sticky fit.
The rose on top is included as a Cura project file the support blocker box removes a large part of the bottom of the rose, and I'm my opinion makes it looks better as well as increases the gluing surface area. I would tune your supports if you are going to print the rose in the orientation it is in. The angle reduces supports as well as provides a sheen that is aesthetically pleasing.
Take aways:
The author remixed this model.