IMHO the very best photograph ever taken in space was during the Apollo 8 mission when astronaut Bill Anders shot a photograph on December 24, 1968 while orbiting the moon. It's called "Earthrise", and is a photograph of Earth and part of the Moon's surface as seen from the command module as it emerges from the moon's "dark-side" to the light side. The way the partially sun lit Earth seems to be hanging there in the darkness of space seems to show IMO how insignificant this planet is in the vastness of space -- and yet it is the only planet we know of that has life on it. Still others have described it as "The most influential environmental photograph ever taken."
In either case, it does show that for us, this small world is the only one we got, and we should do our very best to take care of it, for both ourselves and future generations yet to come.