While the image posted by the OP has its share of problems (eg, yellow, oversaturated, slightly soft, supernova teeth and other blown highlights), and it is good practice to try to help out such problems first, one should ALWAYS follow the physician's rule of "do no harm", ie, don't make it worse.
I spent 95% of my time working on the above problems. Then, once I got the subjects as good as I wanted for this little demo, then dropping in any background takes only seconds. A '60's, poster-like, muted tiled rose (the flower, not the color) background was the 1st thing that came to mind because I knew I had some nice images of roses to use, but there are lots of other backgrounds that might be more to the taste of the OP.
Tom M