With the PublishPress Checklists plugin, you can require that all your posts have a Featured image.

In the Pro version of the plugin you can also require that the Featured image has a maximum and minimum height and width.

This is very useful to make sure your posts look good inside the theme your site is using.


Featured Image Size
Featured Image Size

If you enable these Featured image options, they will be visible when you edit content.

If your Featured image box is the wrong size, these tasks will be marked in red in the sidebar:

Image Checklist
Image Checklist

If your Featured image box has an image, this task will be marked in green in the sidebar:

Image Checklist Green
Image Checklist Green