"Surfing" the web today, I found a nice tutorial on how to decor a mug, or any porcelain surface. It was found here, it's dedicated to Father's Day but it can be used for other ocassions as well.
What you need:
-porcelaine gel and pen
1.Make your drawing with the sharpie
2.Trace around with the porcelaine pen
3.Fill the drawing with the porcelain gel (you will need more than one coat)
4.Bake accordint to the directions of the stain.