In the frontmatter, specify a file name for the teaserImage. This file must be in the /static/images/thumbnails folder. The image should be cropped and resized to 400 x 300 pixels.
For content pages of type observable or interactive, you can add Download Image and Download SVG buttons. These buttons are added automatically when a downloadId parameter is added to the frontmatter.
...
downloadId: viz
...The downloadId must be the same as the id attribute of the <div> containing the svg that you want users to be able to download.
<div id="viz">
<svg ...>A chart or map</svg>
</div>