Tolkien does, however, provide some fodder for inspiration in the origin of orcs — they are twisted elves. Therefore, we can intuit a variety of orcs (and therefore hobgoblins and gnolls) by making them more or less like their elven progeny. While I primarily plan to use these variations for the purposes of making leader and champion types, there is nothing to suggest that there aren't entire tribes of the following:
Warrior MagesThese orcs function exactly as a normal elf, but with a full HD and are the type of variant orc I will most likely use as non-leader types. The spells most commonly used by this type are magic missile, darkness, protection from good and ventriloquism. While they are capable of casting Charm Person and Sleep, these spells are closely guarded by leader types — used in combination, they make for easy assassinations by rivals.
WizardsWho says all the magic-using types that have an orc army at their back have to be human?
NecromancerThis is a variation of the Wizard who specializes in creating and controlling undead. While there are plenty of examples of necromancer-type classes out there, I am tempted to simply say that a necromancer can summon 1d6 skeletons/1d4 zombies/or 1 ghoul at will.
ArchersThese nasty orcs are capable of shooting at any time during the movement phase and may split their move — half-move, fire, half-move.
Finally, there are also combinations of all of the above — Archer Mages, Warrior Necromancers etc.