The World Health Organization recommends they be built a reasonable distance from the house balancing issues of easy access versus that of smell.
The superstructure exists to shelter the user, and also to protect the toilet itself.
The decoration on the outhouse door has no standard.
The well-known crescent moon on American outhouses was popularized by cartoonists and had a questionable basis in fact.
Others, often in more rural, older areas in European countries, simply have a hole with two indents on either side for your feet.