Hello Camille,
Thanks for writing in!
http://demo.theme.co/integrity-4/ is using Blank - No Container | Header, No Footer page template. The content area does not have any contents either. The images were set as a background images of the page.
You can check out more about the page templates in the theme here:
To know more how you can insert background images on a page, you can check it here:
This is also possible with Pro theme. As long as you do not have page content or the page content is shorter than the browser height, the page will have no scrollbars. Scroll bars will likely to appear when the page is to long to display in a browser.
Hope this helps.