The cover picture of your Ghost blog can be set in the editor under "General". In order to display the whole image, it is recommended to accurately crop the image.

With the recent major update from Ghost to version 3.0, the design of the Casper theme was also improved. This also slightly changed the size of the publication cover.

Ghost editor settings to set publication cover
The publication cover can be uploaded in the settings of your Ghost blog.

Even before that it was possible to select basicly any image as a cover. Depending on the aspect ratio of the picture, more or less of it was actually displayed.

Cover of different games for a perfectly fitting Ghost blog Casper theme
The number13 cover image fits perfectly into the frame of the homepage.

To create the perfect cover, you want to know which aspect ratio the optimal cover must have. Since the cover adapts dynamically to the width of the screen, there is no 100% answer. However, it can be assumed that most monitors have a 16:9 format.

How to Resize Images on Windows and MacOS
This guide will explain why it makes sense to scale images on websites and how to do it on Windows and MacOS.

For this format, the optimal size of the publication cover is 1900x400 px, which corresponds to a format of 4.75:1.