1. ok custom rules are acceptable for all ranks; however, if they include the word death, demon, angel you must be S Rank to use such an alias.
2. There are some Aliases that still can be used for many ranks
Knuckle Headed Ninja-Gennin-S Rank
Pervy Sage- S-Rank
The Copy Ninja- S Rank
Leaf Villages Burning Lotus Flower- Chuunin
The Demon Holder- Jounin
Sand Bearer- Gennin-S-Rank
(More to come)
3. If the alias is innapropriate the admin will give you another chance at it if not an admin will give you the alias of Banned Alias...which will be put among your rank above your avitar.