I like the idea of making our own world, uncharted, and not yet touched by the characters we've created, or even the creatures we set in the land. Granted, there may be a few creatures, and human-like species there, but the main idea is that we explore the world, and see what all is there for us to use, be it wood for fires, animals for food and clothing, or even entirely new civilizations we come across, and have to fight off, or invade, for us to have any power. Tribes of native people, wild animals defending their territory, or even street gangs trying to use us as their betting slips, and each side trying to persuade us to pick their side over the other. Everything is permitted.
The idea I have in mind is in our own section of the universe, where only the captain, crew, and moderators have a say of what kinds of things are there, from a forest type of setting wonderful enough to put even the Garden of Eden to shame, or whether it's something like our own planet was, back in a certain time period. Everything, and I mean everything is only limited by what we can imagine, so this will really put the wheels in motion, and get our creative juices flowing.
The new world we have, will be roughly six times the size of our own planet's, but it will have everything needed to support life, so if we want to add in forests, rivers and lakes, mountains and volcanoes, or even something a little more unusual, like a rainbow colored sky, with black clouds, and a red moon, or something like three eyed fish, talking squirrels, and other things, than by all means, add those as well. Remember, the only limit is what your imagination can do, and think of.