First you have to make a narrow selection on your picture. I lowered the opacity of the original picture here so you could see the narrow strip a little better. Once you have made your selection you'll want to copy that selection on to a new layer. In PSE you would right click and choose layer via copy
On the layer with the narrow strip you are going to stretch it across your canvas. First do one side then the other until the entire canvas is covered with the stretched strip.
Now you can move the original picture above the new pixel stretched background
To finish it off, I added an outline around the original picture on a separate layer. Then I erased parts of the original picture to let the background show more. And finally merged the layers together