Such a love of mine, whether in black&white or color, indoors or outdoors, a simple black background can make a portrait and can be achieved with out the use of artificial back drops.Placing a child by a window with strong light allows the wall in the background to go dark and makes a great simple black&white portrait. Above Abby was in her families diningroom which had deep brick colored walls which when converted to black and white the wall looks black.
If the room has shutters or curtains opening just a portion to allow enough light to come through and illuminate your subject. Above, Ms. B. was in her diningroom with all indoor lights off and one of the plantation shutters on the rooms windows open for just the perfect amount of light need, shutters are great since you can change the direction of the light coming through.
In an outdoors setting a dark or black background can be achieved using a shallow depth of field and making sure there is no light hitting the background , the photo of miss K. above was taken in their backyard, a fence and some bushes were behind the her in this photo.
Again another outdoor portrait this time shot with a focal length of 200 at 2.8 to drop out the background which was a group of trees, the subject was lit by light coming through a break in the trees, awesome!
Here is an example of a controlled setting with a black cloth background and a large soft box lighting Baby S. due to the 5 inches of rain we received that day, this look can be achieved with window light if the weather permits.