You need to make custom particles to do that. So create a comp 200x200 and create your star with an X. Bring that into your main comp and turn off it's eyeball. Create a solid, add Particle World and change the particle type to textured square. Open the texture Layer and choose your precomp with the star.
"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.