My first design was based on the UN Flag with the wreath for peace, but the stars represent the continents and the male and female symbols represent humanity.
I also thought this looked too much like an international organisation flag particularly the UN. So I based another design on the land/sea ratio of the planet. This is simply a blue flag with a green field on the fly and the Earth Symbol.
The reason there is more blue than green is because there is more water than land. I was also unsatisfied with this a put the green end at the hoist and the symbol so that it includes both green and blue.
As the moon is supposedly claimed by man I also designed a moon flag. This is a black flag with a white disk over a blue disc symbolising the moon of Earth. In the canton there is an Earth Symbol symbolising its sovereignty to the Earth.