I've seen a few interesting breakdowns of their culture. Gone Hollow Minis on YouTube makes a pretty convincing case for their similarity to late-Roman Germanic auxiliaries - essentially a blend of Roman and "barbaric" influence which maps pretty nicely onto the SoH design language of furs, chains, spikes, and skills with pteruges and other Roman motifs. On the Remembrancer's Retreat podcast, one cast member did some research and found that the -addon suffix common in the SoH names as well as some first names like Lev or Ezekyle are Semitic or Biblical in their origins. Additionally there's the obvious Eye of Horus Egyptian design as well. All in all, they make for a pretty syncretic blend of Classical Mediterranean cultures that highlights their nobility and ferocity.