The Elite range has only one Triari pose - and it's a bit limited. Basically a guy kneeling down. Then I noted that the hastati and principes figures were equipped very similarly, the only point of differentiation being that they were armed with a pilum rather than a hasta (or "spear"). I am going to try arming some hastati with the hasta to make up the second and subsequent ranks of my triarii.
As I hope you can see in the accompanying picture, they make a convincing shieldwall together.
Looking at the picture, I wonder how the guy wielding his weapon overhead might look.
I've another two dozen on order from Elite Australia at the moment, so I ought to be in a position to perform some experiments soon.