In your portrait the person is the main point of interest, by using different backgrounds and placing them in different contexts you can dramatically alter the mood of a shot. 

Sometimes it is best to keep the background as minimalistic as possible, other times it can give you and extra depth to the character you are photographing. The key is experimentation to see what works.

Here are a few examples of how backgrounds can change the mood of photographs, why not have a go and upload your photos to share with others?