Clown tattoos are generally meant to symbolize what clowns in general are symbols of; humor, and an ironic mockery of the seriousness of life.
Although many clown tattoos feature a more modern facsimile, others show older depictions of jesters and mimes. The jester often shows a spritely figure in a tight body suit that regularly sports large diamond shapes, or rounded spirals. Their hats and shoes have long pointed tips, and their faces usually show makeup that is similar to their clothing in design. Mimes can be used for a more noir piece, as their colors are most commonly black and white. They can be placed in recognizable poses, like trying to escape from an invisible box or even dancing.
Modern depictions of clowns in body art usually show one of two things; the gentle, innocent clown, or his evil counterpart. Kinder clown tattoos often feature the busts of these gaudily made-up characters, with bushy wigs and spotted, baggy clothing. Full body or bust, they are often placed alongside balloons (which can be shown floating to different areas of the body), piling out of an under-sized car, or teaching a small, tutu wearing dog to do tricks. Scary clown tattoos show a similar appearance; however, they wear more ominous features, such as large, pointed teeth (often covered in blood), glowing cat eyes, and creased brows. This style also commonly features things like flames or writhing snakes for hair, weapons, and skeletal or demonic characteristics.
Many clown tattoos depict a likeness of a popular character. Bozo the clown, of course, is one of the most recognizable, but there are several obscure, yet equally interesting characters that you may use. Two interesting ideas would be the clown Cepillín with painted beard and eyebrows, red nose and large, white lips; or a stylized version of the well loved tramp clown Emmett Kelly. This style is generally quite realistic in design; however, you could easily take any of the real life characters, and create an old-timey circus poster design. These are generally very bright in color, and feature the clown at the height of his performance.
To many, the clown is an object of fear, as their appearance is something completely out of proportion to reality; to others they are an emblem of innocent fun. However you choose to depict this character, you will without question make an impact on every person that sees it.