That reminds me of some novelty drinking glasses I used to have. They were a set of four and each featured a photo of a different woman wearing a black bikini. Add ice and a cold drink and the bikinis would disappear. Of course, I didn't know those ladies.
Your idea sounds amazing! I'd love to make a cup featuring my wife! (Maybe even a set of four!)
Any chance we could see a before and after pic of that mug?