You can decorate your body with tattoos in parlors. There is a wide selection of patterns for all parts of body. New tattoos are unlocked along with ranking-up or they are given as awards - this how to get a unique pattern. There are 6 tattoo parlors in the game.
Los Santos Customs
You can customize your cars in Los Santos Customs, a custom car corporation. Almost everything is customizable. From respraying, through adding an improved armor, to implementing turbo, which improves the car's performance. You unlock car improvements through ranking-up and winning races limited to a particular car category. Moreover, in LSC you can mount a tracker and sell cars. There are 4 Los Santos Customs shops in the game.
Here you can change your hairstyle as well as facial hair. New hairstyles are unlocked through ranking-up. There are 7 barber shops in the game.