Changing Particle texture in particle system in c#

I have 1 particle system and 4 different sprites
Depending on some input in want to change the shape op the particles trough script.

At this time I can set the shape of the particle by dragging one of the sprites in to the particle texture (shader: mobile/particles/Additive) SEE IMAGE*
I could make 4 different particle systems but that doesn't scale very wel if I want to add more or if I want to change the properties of the all particle systems.

id like to do something like:

public Sprite[] imgs;
public Gameobject particleSystem;

public void SetParticleShape(int n)
{
Gameobject obj = instanciaste(particleSytem, transform.position, quarternion.identity);
obj.SHADER_TEXTURE = imgs[n];
}