So I was playing Battleheart on my iPhone... kind of obsessively (hush, Kainenchen)... and the particular way that the power level of the skeletons advances gave me a few ideas. I really like something about the idea that undead from this one particular canyon, swamp, or whatever have different powers than undead from other places, just because of that origin. The ideas that followed are available for anyone's use, if you want some flavor text to back up the varying powers and power levels of undead that are nominally the same type.
See, the actual function of animate dead in D&D 3.x bugs me just a little. (This is also topical to 5e today: see here.) The function of this spell and the skeleton or zombie templates means that all human skeletons are basically the same; if you want a better skeleton, get a better base creature. Don't get me wrong, I like a skeletal T. Rex as much as the next guy. No, the problem is that when human skeletons have a basically fixed power level (CR 1/3). A spellcaster who can animate a graveyard full of your family members... shouldn't bother, if facing opponents remotely able to challenge him. That's fine, though; WotC designers and third-party publishers have spilled gallons of ink creating new and more threatening skeletal undead made out of humans, and creating new spells that generate that specific undead.
Setting aside that this is sort of cop-out in terms of generating content (that's what you get for paying by the word!), it's also a lot less compelling for players to learn about these spells as a foundation for drawing conclusions about what's going on once the encounter is over. Not everything needs to be a mystery, but anchoring the powers, appearance, and so on of the undead to things in the world gives players a way to draw conclusions. I maintain that players get more enjoyment out of remembering something interesting from three sessions ago than they get from possibly rolling well on a Knowledge (Religion) check to have the GM tell them something that was not previously established (though I don't extend this argument to the point of doing away with Knowledge skills).
Necromancy and the Identification of Skeletons
The Undead in general are differentiated by the circumstances of death, just as the living are differentiated by circumstances of birth. Many forms of undead share their eternal undeath when they strike down the living - particularly shades, wraiths, and vampires. Others, such as the mummified dead, may transfer their cursed state to their victims, ending their own torment at another's expense.
Skeletons, zombies, and shades are the least among the ranks of the Undead; the means of their animation determined which of those three they should become. The reason you bury the dead rather than incinerating them (Editor's note: something I've seen GMs struggle to justify in some games) is that the spirit, when called back to the world, will seek out the most familiar body. If that body rests safely and securely on ground that remains consecrated, the spirit enters the body and leaves it just as quickly. If there is no recognizable form, the spirit is confused and maddened, and manifests as a shade (or possibly a greater incorporeal undead, generally governed by the individual's strength of will).
Skeletons and zombies, on the other hand, are particularly influenced by the place where they were interred - even more so if that location had borne great personal significance in life. Therefore a necromancer might be able to turn all of the skeletons he is animating into Knifewind Canyon skeletons even if he transported the bones from elsewhere, but he'll have much greater success if there were bones there already, of those who had died there.
The skeletons of Knifewind Canyon, as every scholar of the Undead knows, are distinctive for the howling wind that gusts forth from their mouths, and for the river-clay baked around their bones by the punishing sun, which renders them more resilient to many forms of harm.