Placeholder image for image block with dynamic content

If you’re using the new Image block with dynamic content in the Generatepress Content Templates, it would be nice to be able to set a default image to help visualize design a little easier.

At the moment, if you insert an image and set it to dynamically use the featured image, you just get an empty box with a line through it. If you are trying to place additional meta elements over the image, it’s hard because the default grey box is square, which may or may not be the same aspect as the featured images you use on the site.

In this GP tutorial (Block Element - Content Template - Documentation) for content templates, they are able to do this with a dynamic background image on the container. Selecting any image to use while the template is created.

As far as I can figure out, you can’t do this with the image block.