Can other species live on your main world and, if so, how does this go down with the general populace? Does racism rear its very ugly head and, if so, how is this combatted?
What do other worlds think of your main characters visiting them? Does this discovery encourage then to be more outward looking or is their reaction worse? What form does their racism take? How is racism dealt with (and do the authorities react to this willingly or do they have to be pushed to do the right thing?).