While you can do pretty much with your caln there a few basic things to keep them down to earth

  1. Must end with "Clan" or start with "Tribe of,".
  2. Cats must not have additional body features like wings or horns
  3.  Must include types of prey they eat
  4. Must include type of territory they live in
  5. Must have common pelt colors that must be realistic

Other than that all i can say is be Creative!