I’d have slaves in rags, with some of the men bare-chested, like these guys but unarmed (unless they’re rebelling or pit-fighting): LINK, LINK and LINK. Personally I’d find collars or bound hands too limiting for gameplay purposes.
Regarding Barachan pirates, the dog handler on the left in this pack (now OOP, or at least out of stock) is why I wanted to use Dark Age Irish to represent them in 28mm. IMO he’s perfect for representing piratical fantasy-European types with savage, roguish flair while steering clear of all the post-medieval tropes: LINK.
The thought of Barachan pirates as Bronze Age Sea Peoples given a Dark Ages makeover does intrigue me, though. I did at one point start converting some pirates for what I imagine to be the Hyborian Age counterpart to the Indian Ocean out of colonial African bearers/porters with arm swaps and some head swaps. That might be “sorta kinda” close to the Sea Peoples look, I guess.
As for Vilayet pirates, it might be worth pointing out that REH meant for them to be Cossacks. He was really into the idea of Cossack pirates. Still, I wouldn’t constrain myself to that visual so I’d hardly expect of others, either.