Yes, I would keep the wall sconce back plate limited to 5x6 because otherwise it would look like the light fixture is hovering off the wall. Here is a good option. http://www.luxurylightingdirect.com/1LT_WALL_p/try-b3431.htm

The shiny brass would be appropriate on a more formal less country style home. However, the likely reason you do not see polished brass exterior lanterns on the outside of homes is because the metal pits and turns colors over time. To keep them bright and shiny, they have to be removed and polished. Even the lacquered brass will turn over time and have to be sent out for polishing.

We have 3 standard motion detector fixtures (very utilitarian - nothing fancy) on my property that light the way for me at night to a dark backyard entrance to my unit. They do not stay on any longer than a minute or two and are not set off by anything smaller than the deer that also visit routinely. However the deer seldom venture close enough to the walkway the lights illuminate to set them off. And they are completely unnoticeable during the daylight hours.

What problem(s) are you trying to solve? What would be the purpose of a light to the right of the garage door? Is anybody going to walk or stand there at night? There doesn't seem to be a path to the right of the garage leading to the back of the house, just a hedge. Would the garage door be open whose light would illuminate that area when needed? What would be the purpose of the light to the left of the garage? Is there a path from the driveway to the front door? If so, why not use landscape light(s) to illuminate the path instead of the wall? If people walk from the sidewalk to the front door along the driveway, you could add landscape lights along the driveway. Outdoor Lighting Basics To minimize the harmful effects of light pollution, lighting should Only be on when needed Only light the area that needs it Be no brighter than necessary Minimize blue light emissions Be fully shielded (pointing downward)