Something that can add a whole lot of interest and dimension is a kicker light behind the subjects. The great thing about a kicker is that it does not require much finesse to use, since the concept is to create sidelighting and almost blown to blown highlights.
Kickers can be used in 2 and 3 light configurations. If you have two lights, expose the scene with your main light only and use a fill card or reflector as a secondary light source to control shadow fill. Then add the 2nd light as the kicker behind the subject set to some strength that is higher than the main light. With three lights, simply expose with your main and fill, then add your kicker - again on a higher power setting than the main light.
Kickers can require a bit of tweaking to get the perfect amount of back\sidelighting, so play with its aim a bit, but generally it should sit on the floor aiming up. Another thing to consider is if the subject is against a textured wall or surface, the kicker will really help to define that texture. In conclusion, using a kicker will help to add seperation to the background, and add highlights at the edges\sides of the subjects.