Easterlings and Haradrim

[Gormonghast]

I'm planning to make these separate Nations, perhaps incorporating different miniatures, but am a little confused as to the distinction. Most sourses use the terms Easterlings, Haradrim and Southrons indifferently, yet in the books they're clearly different peoples.
I assume the LOTR miniatures represent Haradrim, but what do the Easterlings of Rhun look like?
I've seen images of anything from Ottoman turks to Black Huns, but is there a definitive description anywhere?

[Malacandra]

There's a mention somewhere of burly bearded Men almost like oversized Dwarves, wielding axes; but I'd have to comb through the early chapters of Return of the King to find it, I couldn't see it on a quick skim through The Battle of the Pelennor Fields.