Great job so far. I am totally cluless about particles myself, but I do know what I like to look at. The particle effects seem good so far.
In addition to Modron’s comment about the mouth materials, you might want to look at the teeth. I’m not a big enough fan of Dune to know how the teeth are supposed to be, but they look a little too geometrical and inorganic. You could distort the shapes into something less cone-like, or If the shape is the way it has to be textures might help.
Best of luck. I look forward to seeing your updates.