Child Warrior Concepts

Some color filled outlines in photoshop I drew over a sketch; some concepts for child warriors set in a fantasy/post-apocalyptic setting, inspired by the attire of the orcs in the sequel to Middle-Earth: Shadow of Mordor, Shadow of War. These characters reside from different classes or tribes--

The Warmonger Tribe - A class dedicated to warfare and battle tactics
The Marauder Tribe - A band of raiders who live by earning loot and treasure
The Mystic Tribe - A cult who are bound by practices of dark magic
The Feral Tribe - A tribal group who are renown for hunting or taming wild beasts, and eeking a living in nature
The Machine Tribe - An industrial organization where kids build radical inventions and contribute to progress
the Power Tribe - A conquering nation that lords their influence onto others, obtain knowledge and seize property for themselves
The Knight Tribe - An authority movement where honorable warriors bring order to society
The Dark Tribe - A cult that associates themselves with the dark and gothic things that go bump in the night
The Terror Tribe - A terrorist organization that promotes fear tactics and cruel acts of torment to any potential threats
The Mountain Tribe - A traditionalist culture that eek their living in remote environments, living quiet lives in hunting, gathering, and farming
The Outlaw Tribe - A group that yields no specific traits nor allegiance to any other tribe; they are cast aside by others and merely look out for themselves.

The kid on the left is suppose to be a gladiator from The Warmonger Tribe, the center stage star is some pretty looking raider or pirate type character from The Mauraider Tribe, and the last one on the left is a necromancer.

Original sketch below here. --




So what do you lot think? Got any ideas for concepts I can use for characters from their respective tribes; or do you have any ideas for tribes for yourselves? Or any tips on what I can do to improve on my art and have it stand out?! Please let me know.