Try packing all of your sprites into a single texture, then use Set Texture Index with a random index in Init, and Set Flipbook Size in Output with the number of rows and columns in your sprite sheet.
I was setting it up to play multiple random animations (flipbooks). Using the random index tip was great for making them all play staring at random frames, but I could not figure out a way to have multiple flipbooks randomize into a single particle, so I duplicated the entire chain for each.