One fragment per geometry

I have a particle system, and I want to differentiate every particle in a sprite sheet fashion.
I was wondering if its possible to use a fragment shader instead of a image sequence. Every particle will have an instance of the fragment as ‘texture’ but with different uniform values. Passing a couple of attributes to the fragment to add variability beyond the image sequence.
I guess its like a draw instanced method but on the fragment instead of the vertex.
Is something like that even possible?