You can atlas your textures. And have like a bunch of different mushrooms in the same material. Not only its way less complex than doing diff materials on the same emitter, but its also much more efficient on the performances.
Think of it exactly like how you do an animated texture sequence. Except each frame is a mushroom texture. And you don’t cycle through frame but pick a random initial frame for each particle spawned.
Essentially, if you know how to do use a flipbook texture, you know how to do this