You can use marbles (or other small balls) to create starbursts. You just rubber band them into the shirt and they will look something like this:
Leave them in all the way through washing the shirt.
Here's a tutorial.
Here's a few I did:
Do NOT remove the rubber bands or string until AFTER you've put the garment through the rinse in the washing machine. When you're all done and the shirt is dry, iron with a hot IRON.