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:
The hide comes as a complete side of a cow or shoulder, approximately two square metres.
The piece is cut to size and, after the sketch is drawn on it, the lines are cut into the leather with a swivel knife.
The drawing is then carved into the surface with a variety of tools.
Finally, the piece is dyed using spirit-based dyes by painting and rubbing on with cloth or finger.