Room Tone
Normally when mixing a film or TV project you want the room tone of where the actors were so you can match it up and creat a smooth audio track. If your being creative with room tone like it seem in your posting keep in mind what roomtone is. If for example I'm in a kitchen, room tone may consist of a fridgerator compressor kicking, a fan blowing in the backround, a buzzing light overhead! Look at your video footage carefully and asses what is in the room to help build believable room tone. good to have a master file of all the room tone elements separate so you can manipulate as your cuts change, (long shot verses close up etc).