I've just recently started a campaign of my own. What made this game really different and fun for me world building wise was that I tweeked the background rules a bit. Where in a planet is classified as one homeworld I changed it where one planet can have more than one homeworld choices for different characters.
For instance a made a planet where a player can choose to have been born there and yet he has the option to be a feral, hiveworlder or imperial. How could this have happened? Well the one player who choose to be feral was living underneath the toxic sludge part of the city where many of the other ferals of that planet fight for daily survival. The Hiveworlders where the underclass who had to eek out a living in a routine and hazardous job. While the Imperials where those who at least have some money with them.
Well that's it. Just a glimpse on how my games are being run this days.