Are you giving it anything to work with? Tell it that there’s furniture in the room and there will be furniture…

Sorry guys, my mistake. Turns out that characters created by https://perchance.org/ai-character-generator have a default “Image generation prompt ending” set which includes (resolution:::512x768), which is why it was ignoring my own resolution syntax. Hopefully this will help people if they have the same issue - check what’s set in that field for your characters!