What a great topic to talk about (hattip to Grognardia)... except what a bad topic for me!
You see, I've done a lot to my orcs, and many other beasties in my AD&D world. My tabletop players have ran into more differences, changes and odd things that vary off of the standard AD&D definitions... but there's a lot more they haven't run into or figured out! I can't spill all the beans here So, I will try to give you some broad brush strokes of things they already know and see how we do.
In my Dark Ages campaign:
Orcs - are pig-faced and a bit larger/bulkier than humans. Their genesis is rumored, but the exact facts are lost to history. They are religious zealots, smart, cunning, have no problem with sunlight, are very militaristic, resemble Planet of the Apes gorillas in coloring, dress and armor. They will commit suicide rather than be captured. They remove the heads of their victims after battle, and burn the bodies. They do not leave bodies of their fellows behind. They are extremely racist and view humans and elves as no more than cattle or a sub-species. They may also be breeding hybrids of some sort for some reason.
There are some specific influences to my orcs and some clues here that may give you further insights. Orcs are right now the Big Bad Guys in my campaign and have the players full attention.
Kobolds - the players ran into a strange new type of kobold a couple of games ago - these are winged kobolds that spit poisonous saliva into players' faces. In my campaign, kobolds can climb walls and ceilings like spiders.
Troll Mages - take one orge mage, reskin it as a troll, merge the best of both monsters' abilities together and you have the feared troll that lives under the bridge right outside of Enonia in the Dale Woods. This guy is responsible for one near-TPK and a lot of angst. The players still plan on taking this guy out.
Trollkins - are the "children" of the troll mage. Mysterious and fey. So far, they seem curious and childlike, but extremely wise beyond what seems normal.
Dwarfs - are a lost race. They were once slaves to the Dark Ones (ancient evil beings of Chaos that ruled the lands) but once freed, they've not been seen since.
Elves - are a seafaring race, grouped by families/clans.
Dragons - are generated using EG Palmer's amazing Dragon Generator. First published in 2009, I have a copy of that in my "Best of Old School Blogs" folder. Now that is probably news to my players that dragons will not be dragons, but they'll learn soon enough. My tabletop players are already familiar with one, even though they don't realize it... or maybe they do!
One thing that is common for all my monsters. Unless otherwise specified in the Monster Manual, they're intelligent, ruthless and committed to their own best interests. They don't particularly fear the players. They have their own agendas and I prosecute those agendas to the best of my ability.
This has caused some issues, and led to one player being asked to not come back when he couldn't deal with the changes. In his mind, kobolds should be groveling at the feet of a first level character. In my mind, these are starving kobolds who are desperate enough to try and bluff their way into robbing the players, as far as they can, because they have NOTHING ELSE TO LOSE! I'm very proud of the players that I do have that were able to deal and adjust to the world as I've presented it. I think that's something to be aware of when you alter from the "norm".
I'm looking forward to reading the other entries in this meme. I hope you've enjoyed mine and if you have any questions about them, just ask! Stats are available - feel free to email me. Bryan, close your email, I won't send them to you. :P