A lithophane box that holds 4 lithophanes and a 9 led light in the center. I used this website http://3dp.rocks/lithophane/ to convert images into an stl file. Before converting selected images to stl files, make sure that the images are a size of 632x600 pixels. It is very important that the images selected are this size, as the lithophanes will not fit after printing.
When uploading your selected images to http://3dp.rocks/lithophane/, click on the Settings icon on top of the page then on Model Settings and change the Maximum Size (MM) to 150. Next, click on Image Settings. You should then see settings for positive and negative image at the near top of the page. Make sure you have the positive image setting selected. When you are sure that all of your settings are correct, click on the Model icon on top of the page to start converting your image to an stl file.