Somebody across on the Impetus Forum painted up some Hyrcanians for use with Hellenistic/Parthian armies
http://impetus.ativiforum.com/t467-my-take-on-some-hyrcanian-infantry-inspired-by-you-jim#3693
My own feeling is that if it looks right, it most probably is right, but we can see what Duncan has to say.
Very nice painting job.
Well, we know little about how the Hyrkanians dressed and fought, except that Herodotos back in the C5th lists them among those peoples dressed and armed in the same way as the Medes and Persians. There is no reason to assume that in later centuries they parted company from this general Iranian pattern, so for Hellenistic-era Hyrkanians these guys look fair enough. I don't think I would personally mix Argive shields with thyreoi in the same unit, but that's not a big issue. Very nice painting, as Patrick says.
Based upon that recently discovered Parthian sculpture thureoi might well be the most likely shields .
R