Just select what kind of fill you want to change the page background. If you are using an image, you can choose to aspect fill, scale to fit, or tile if you have a repeating pattern like in this ...

How to change your Instagram Story background color if it has an image or video. Most Instagram Stories include a picture. But unless that picture fills up the entire screen, there's going to be ...

How to change your Google browser background image. Note that this will only change the background for the New Tab page, which is the page that loads when you open a new blank tab or window.