ideas: guts explosion. The one that would explode debris using physics and blood splatter. Also when debris hits any colliders, it leaves blood decal and dies (gets removed). You could sell that well
I bet if you did arcane/magic pack that incorporated a lot of the elemental stuff you already have, it would be a good seller; everyone seems to love the RPG-related assets.
eg) Fireballs + explosions, meteor, energy shields, portals, arcane energy beams, lightning, frost/ice bolts, wind/tornados, healing effects, stuff like that.
You could probably do that with script, too… I think a particle’s energy starts at max and decreases to zero where it dies, so you could write a script that monitor’s a particle’s systems particles energy values, and switch their particle texture as they approach zero. Never really played with particle systems, but its worth a shot.