I like where you're coming from. There's also the Pro and Am decals from the IMSA and/or Blancpain series. I personally use a Logitech logo and a decal of a steering wheel graphic to show I'm a wheel user, even if some people don't get what it means.
IndyCar (and maybe others) use a yellow number on the rear for rookie drivers. I remember they made a big deal about Alonso, a two-time F1 champ, having yellow numbers on his car at the Indy 500 last year.