Above my pay grade. It's not tech support or judging coordination. I'd say in the end it's up to the individual judges to decide if it fits the "setting" theme or not. I only step in to read and judge entries if there's a problem or a tie.

For me, personally and unofficially, when I've done Prep in the past, I usually made it a story (well, a vignette anyway) with at least one character who is, for example, looking around a room and noticing (and hearing, smelling, etc.) things. But I honestly can't remember if I ever won a Setting contest round or not, so please don't take this as official advice; I wrote for my own benefit more than to please judges.