After installing the demo content there might be missing author images. You can simply replace the author images from the ghost admin panel.

https://support.themeix.com/wp-content/uploads/2022/08/image-1.png

At first open your Ghost Admin, then go to the Settings > Staff

https://support.themeix.com/wp-content/uploads/2022/08/image-2-1024x485.png

Now replace the image for the staff user.