It's a shame we can't replace the background with a suitable tile for a given banner (if provided with the banner)... As so far (IMHO)
aahhsin's last banner (without the not-so-nice blend attempt) actually does feel "fall" / "autumn" like. Not the best banner, technically, but definitely fits the theme for me.
Maybe we could consider such an option next time, as we've got rules for this one already and I wouldn't want to move the goal posts so late into the game.