This glaze looks pretty cool and possible to do. Maybe put a thin line of wax resist under the outside line so it really pools relatively evenly. If the glaze is heavy enough then it should melt over the line and that would look even more awesome.
Porcelain bowls designed by Geraldine de Beco for Bernardaud in France. When the bowls are filled with a liquid, the image of an animal is formed (cat, dove, wolf). These are bowls, but I would love a mug like this!