One of the premises I have always worked under is
"It's not what can you carve, it's what can't you carve?"
The answer being pretty close to nothing. I've even seen some amazing things carved out of toothbrush handles! It's a massive task to give detailed information on everything that has ever been hacked into by someone with a chisel or a chainsaw ... but here goes!
The following is a brief description of what you can carve:
|Horn & Shell