Hello Christine,
By default, the background image is set to appear on every page for consistency. However, this can be changed with a child theme. WordPress pages are controlled by templates. Instead of the applying the same template to each page, you can create a specific front-page template that meets your needs. It is safest to do this kind of modification in a “child theme,” that way you can still receive updates for the parent theme without erasing your changes.
Best,
Christopher M.