Here is my experience as far as a motorcyclists who wave goes:

Sportbikes: They usually do the peace sign as doulos says, and they sometimes nod their head, even if you ride a scooter. However, I have never seen them wheelie. Probably since I live in a city that doesn't offer much space for wheelies due to heavy traffic.

Japanese Cruisers: They usually don't notice you unless you pull next to them in a lane.

Scooters: They usually wave, although I am uncertain if it is in fear or admiration.

Harleys: Harleys never wave if your riding something japanese. They will probably wave if you're on something American, like Buell, Victory, Polaris, or other Harleys. And possibly if you are on something European, such as BSA, Triumph, or even Ducati or Aprilia.