I was always miffed that you were expected to put three rippers on each base but the Nid sprues has so few. To get around this I have detached the rippers I had and have mounted one on each 40mm base. To fill the base up I've added Nid eggs. I had a little space in the mycetic spore mold and a little Nid egg fitted perfectly! I've also added a couple of little spines to the bases as if spore towers were starting to take root and grow.
With the codex containing the Parasite character it seemed to me that a ripper style army could be fun!