Another overlook area to detailing is the trunk of a vehicle. Most trunks have to very thin outdoor type of carpeting. Vacuuming this type of mat can be long task to maintain to it's new condition. The best solution for this is to remove the mat & use a air hose & force the remaining stubborn debris away from the mat.
For those extra points with gaining the customers trust, you can mention that you could also repaint any inside portion of the inner walls of the trunk area that may be scuffed down through the metal. Your normal spot painting will come to detail here.