Custom Headers

I am using the Viewpoint theme for this site: https://diverticom.com/en – the theme has a setting for uploading a header image, and it is using it for all pages. I am looking for a way to change it on certain pages, especially the blog. The theme has a blog template I am using (https://diverticom.com/en/blog), but I can’t find a way to change the header image on the blog or in the blog template.