You can control what image backgrounds you want to use for your website. You can change your template's background and upload your own image if necessary.
To change your background, please refer to the steps below:
Log in to Plesk
Go to Websites and Domains
Click on Site Builder icon
On the Site Builder page, click Settings icon and select Background
On the Background Properties page, you can select a color, image and its position. You can select what background you want for each page or you can choose the same background for all pages on your website. You can also change and upload your own image for your Secondary background.
After you're done choosing and selecting the background images on your pages, click "Apply" button to save the changes.