That's very impressive. Having not seen one before have just Wiki'd it and found this:
The word lithophane can be broken into two parts to get its meaning. It derives from Greek ‘’litho’’, which is from ‘’lithos’’ which means stone or rock, and ‘’phainein’’ meaning "to cause to appear" or "to cause to appear suddenly".
Your video catches the suddenly appearing bit really nicely. Must find a real one of these to look at. Congrats.

John