My Orcs were pretty much ripped off of Klingons, particularly the bits about talking all sorts of smack about honor, and then spending the majority of their lives stabbing each other in the back, poisoning their leaders and dealing behind the scenes with their hated foes.
Wrath & Rage (from Green Ronin) had an assortment of interesting ideas for orcish variations, none of which I remember that well, but kinda/sorta like;
Orcs adapt. If you wipe out a tribe with fire magic, ten years later, a new tribe with fire resistance will have cropped up. (Also a common assumption in GURPS, where Orcs had a random 10 pt advantage, which was night vision for some tribes, natural armor for others, keen senses of smell and tracking for still others, usable fangs, etc.)
Orcs are degenerate members of other races, and, like Firefly's Reavers, are only 'strong' because they are feral and insane. A pack of 'Orcs' might include some elves, some humans, and even the odd halfling, all raving freaks with greenish-brown tinted skin, as a result of whatever fungal condition makes them this way. Captured members of other species can be turned into orcs by exposure to this slime that grows in their caves.
Orcs are a plague upon the land, sent down by the gods, or perhaps just one god, of bloody slaughter and forever war, to both challenge the civilized races, and to keep the wild places wild.
Orcs are like WoW Tauren, all shamanistic and nature-worshipping Native American pastiches, with totem poles (and totem animals, and totem warriors, and berserkers who turn into real bears) and teepees and coup sticks and howling feather-headressed-warriors riding across the plains on big painted horses.
Orcs are primitive humans, replacing neanderthals / cro-magnon in the setting.
Orcs are living embodiments of rage, all possession Rage and Ferocity like traits, and being consumed by hate, anger and simmering (barely, if at all) suppressed violence at all times.
Orcs are living embodiments of fecundity, and orc females produce prodigious broods of young, mostly males. Going way to the extreme, Orc females might be enormous bloated hags (perhaps even using actual Hag stats!), the size of Ogres, with a half-dozen breasts, as they produce young in litters. These 'mothers' remain in the caves and lairs, pumping out warriors, and have the powers of Adepts and / or Sorcerers and / or Witches (perhaps even Clerics or Druids, in other cases).
Orcs breed with anything, and a 1/2 Orc template that gives pretty much any critter a +2 Str, -2 Int and Darkvision is strapped onto various creatures in the area, including the domesticated wolves, horses, etc. that the Orcs use as beasts of burden and hunting animals. Full blood Orcs get a +2 to Handle Animal or Intimidate checks against 1/2 blood, allowing them to better tame (or cow) creatures whose bloodlines they've tainted with their own blood.