You can apply textures to particles using the same method as applying textures to 3D objects and text. You can also set its texture mapping using the Texture menu.
To apply a texture to a particle stream of spheres:
A texture is added using the currently selected media and is parented by the particle generator.
For example, the following shows the schematic and the result of a particle stream using spheres and a reflection map, making each particle resemble a glass ball.