Hi!
The orcs are a nomadic race led by their dark god Gorath. The orc infantry are lightly armoured and unlike the GW orcs they are brown skinned.
Some of the unusual choices available to the orcs include great orcs (massive mutated orcs, much like ogres), Goraths chosen (somewhat larger and more aggressive versions of normal orcs with better armour and equipment) and Ghost Warriors (orc cultists who are possessed by spirits). They also have access to a variety of lizard mounts.
The orcish race has no spell casters as all their shamans who could use magic sacrificed themselves to free Gorath They do have Shades, ghostly spirits of their shaman as well as lesser shaman who can deal out potions to their troops.
The goblins are taller than the usual goblinoid from GW and have yellow skins (more like hobgoblins) and have been a slave race of the orcs for generations. Freedom fighters are escapees from the orc hordes and consist of a fair sized rabble of goblins supported by the occasional marsh troll or gigantic insect. The goblins also have access to backstabbers (a sort of goblin assassin), shaman (with a more voodoo sort of magic involving curses than the usual greenskin spellcasters) Again they have access to lizard mounts and the occasional lesser goblin swarm.
The barbarians are the last of the truly free humans left in Leviathan and consist of the usual fur clad over muscled types of Conan fame. They also field Warpers, barbarians who can focus the Earthpower to warp their bodies like those from Slaine.
The barbarian druids can raise elementals of several varieties to aid them and the cavalry of the barbarian raiders are made up of huge pigs called razorbacks.
The dwarves have survived the apocalypse by barricading themselves into their subterranean strongholds and moving into the industrial age. With the depletion of their supplies they have opened their gates to explore the new world. The dwarven battle force consists of sturdy warriors, crazed alchemists, armoured engineers and oathbreakers (shaved dwarves with explosives strapped to their bodies!) They also have access to a large assortment of steam driven automatons and war engines.
Elven Slavers are the degenerate descendants of the true elves. Drug addicted and demon worshipping they are few in number but have powerful weapons and equipment, such as power lances and heavy armour. Also fielding a number of nasty demons and possibly some slaves too along with mutated dragons as war mounts.
Light elven scouts are the few remaining true elves not effected by the coming of the darkness and fall of their kin. Generally a bit grim looking they are not the elves of Tolkien. With special troops ranging from firekin (elves with elemental control of fire) to dream warriors (ghosts of dead ancestors) as well as the more usual elven spearmen and archers.
Knights of the Eternal Light are templars with mechanical right hands allowing them to field a variety of unusual weapons. Backed up by more regularly armed retainers and squires. Templars also bring golems into battle in the form of ruined statues and the occasional witch hunter.
Children of the worm follow the great Worm in the southern desert and are a force of undead. Ranging from the children (more living looking troops) to the cursed and risen (zombies!) the children also have access to an assortment of nasty undead type monsters, along with burrowing worms!
The pitiful human rabble are the remains of the populations of the human cities. Many are mutated to some degree and act more like a goblin force, relying on strength of numbers to carry the day. They do have a few big beasts ranging from large mutant monstrosities to great hounds!
Hope that gives you some idea as to what the forces consist of!
All the best!