Thank you, I can't wait to see it! It's pretty simple if you use photoshop. Just go Select>Color Range. Then hold Shift and select all the white areas and delete them. Then make a copy of that layer and change the top layer from "Normal" to "Multiply". Now you have yourself just the frame to work with. All you have to do now is just make a layer in between and start coloring away!
Haha, this is so cute and it really works. The only "complaint" I have is that it's a bit unclear what's going on with the sky and sea(?) and (clouds?). If I were you, i'd probably settle for a flat sky and a flat (brighter) sea, to keep the focus on the moon-heart.
Well, what I was trying to attempt was to make the heart shape subtle. As if a patch of cloud moves across part of the moon, it slowly shows a hint of a heart shape. Also, my focus was on the couple, not the heart.