Why don't we create lots of tables. If there are 6 I roll a d6 to choose a table then roll to select an entry repeat then roll again on a random table.
Yeah, I'd fully expect anyone using them to roll a few times, say "Sword and Sorcery and Space Opera? That's Star Wars, roll over" alternately, "No, that's dumb."
Sometimes when the choice is made for you, you suddenly realize that one, you don't like it and what your choice should be anyway.
edit:
Roll 1D6 and choose the role of humans
Table 1.4 1 Humans are the only character race 2 There are no humans 3 Humans are dominant, other races rare 4 Humans are very rare (endangered?), other races are dominant 5 Humans only slightly dominant, other races nearly as powerful 6 Other races are dominant but there is still a significant human population.
I suggest modern-day apocalypse, where gravity has reversed suddenly and inexplicably. The survivors cling to ceilings and trees and try to start anew.