I turned a painting of a ship into a lithophane, and then splitted it up into a puzzle using Blender. Blender's boolean operations are not that good with very complicated shapes, so a lot of manual fixing was required.
The pieces should be printed on their side, because that way they will be better quality. After that they can be assembled into the image, and then glued onto a sheet of paper. I used normal printer paper. Then you can put it up against a candle, lamp or window.
On my print the seams are very visible, but the better your print quality, the less visible the seams will be. I also recommend sanding down the edges a bit.
The pieces are in no particular order, but rotated incorrectly. Most slicers have a lay flat or a place surface on bed function, so reorienting them isn't too difficult. If you have a moving printbed, I would advise to align the pieces according to the direction of movement. (see third picture)