This is kind of a rehash of this post but that one was made with some notable gaps for the current campaign because it was written for a different region of the Wilderlands. Some of the information from that post is restated here and some of the information is omitted because of the lack of influence of those peoples on the CSIO.
Note that any PHB option from 5e is available in the Wilderlands, these just cover the more unique options of the CSIO.
There are several different types of funny colored humans in the Wilderlands.
Alryans are the dominant ethnicity of the City State of the Invincible Overlord and the nearby settlements. Like their sister race the Altanians (see below), they are descended from the ancient Orichalcans, though their bloodline is much diminished. Their skin is often ruddy or pale pink and their material culture is similar to the later days of the Western Roman Empire. They exert little control on the regions outside of their cities.
Altanians are red skinned (ranging from rusty clay to coke can) barbarians from the jungles of Altanis, though they are common in the lands directly south of the City State of the Invincible Overlord. Like their sister race the Alryans, they are descended from the Orichalcans who ruled the Pazidun Peninsula before the kingdom of Kelnore. Now they live in tribal groups and hunt the ruins of their glorious past. Alryans, Antilians and Viridians often use them as slaves, and they may also be found throughout the Wilderlands of Swords and Devilry serving as mercenaries and body guards. Women and men are, unusually for the Wilderlands, more or less equal among these people, but women more often fill spiritual roles while men fill martial ones.
Antilians are the inhabitants of the city of Antil, though their merchant ships may be found slaving or selling slaves in nearly every part of the Wilderlands. Men typically shave their heads and wear outrageous sword & sorcery badguy armor rather than anything practical. Women are typically not allowed to venture into broader society, being confined to sections of their father, husband, or master's house. They are known for their highly sexist society and their hatred of Amazons.
The Dunael Woodfolk are long-lived humans that originated in the area around Tarsh. However, most living members reside in the Dearthwood thanks to an oath to patrol it made long ago to an Orichalcan King or previous Overlord. Some claim they have elvish blood, but other than their affinity for the forest and centuries long lives, they have very few physical features in common. They are dusky of skin and dark of hair, and their material culture is... look they're just the Dunedain, ok?
Reavers and pirates originally from the Great Glacier north of Valon, the Skandiks semi-recently moved south and conquered the area east of the City State. In even more recent times a Skandik warrior named Bjorn was elevated to demigod status through unknown means and became Overlord after the destruction of the city by an unknown agent. Because of his campaigns, the Skandik kingdoms of Croy and Ossry were united and are now client states of the City State.
TharabiansThese barbarian people originally hailed from somewhere north of the Valley of the Ancients. They were invited several generations ago by the Viridian Emperor to serve as mercenaries against the peoples that would one day found the City State. Since then they have settled land now known as the Tharabian Coast, and for many generations a member of their race held the title of Invincible Overlord; however, with the ascension of the Skandik Kingdoms the Tharabians have largely moved into Viridistan and returned to the service of the Viridian Emperor. They are swarthy and their material culture is a mixture of Celtic and Scythian.
These are the descendants of the inhuman True Viridians and their Ghinorian subjects in the City State's rival empire of Viridistan. Since only a few True Viridians exist in the world, the "common" Viridians have taken over most of the administration of the empire and the temples of their terrible fish god, Armadod-bog. They resemble the Persians of our world, particularly the Sassanians, but their greenish skin and fantastical weaponry would immediately show them as being not from Earth.
Non-human PC Races
These races function as their D&D counterparts except where noted below.
Most Dwarves in the North hail from either Thunderhold or the recently reconquered Majestic Mountains. As the picture implies, they are more or less like the dwarves from the Hobbit cartoon. The stats for Hill Dwarves represent those from Thunderhold while the stats for Mountain Dwarves represent those Dwarves from the Majestic Fastness.
All Northern Elves possess blue skin, though the "high" variety tends to be more of a deep blue while the "wood" variety is kind of a blue green. High Elves are likely from Valon or from some other bastion of the old elven kingdom in the Elphand lands. "Dark Elves" of the Wilderlands are albino.
The First Men were created by a long dead reptilian empire in order to fulfill a prophecy that the world would be dominated by "Man, who stands up like an ape and has the heart of a dragon." The result looks rather like a mandrill or baboon crossed with an alligator, but the use of dragon parts allows them both access to breath weapons and to powerful sorcery. Statistically they are the same as Dragonborn in 5e.
Gnomes in the City State are most commonly from Lightelf, a nearby settlement under the yoke of the Skandiks. These gnomes are similar to the Tinker variety, and have shunned magical prowess in exchange for arms training.
Halflings are Hobbits, though both stout and lightfoot varieties are found in the Wilderlands. They are common in the immediate areas around the City State, where they often serve as peasants on the holdings of Alryan Knights given appanage by the Overlord. They are more common in the area east of the Winedark sea such as Tarsh and on the Ebony Coast.
The ancient Markrabs, a long extinct race, bred many of their servitor demons with human stock. The descendents of these mating experiments still exist throughout the urban areas of the Wilderlands, and new parings are still made in the distant Demon Empires of the South.
Non-human(?) NPC Races
Amazons are a strange race which sages believe was created many years ago by a strange wizard named Lurr. He supposedly saw a vision from a distant world depicting a savage warrior woman, and decided to construct his own for reasons I'd rather not get into. Amazons produce with gynogenesis and thus are all identical in appearance, resembling the woman of Lurr's strange dream. They are all female and almost all powerful warriors. One is said to rule the Orcs of the Purple Claw in Dearthwood, and a large group of them serve the Skandiks in Shield Rune.