Wordpress creates new image sizes only for the sizes that are smaller than the uploaded image.

If an editor uploads an image that is smaller than the pre-defined sizes, then only the sizes that are smaller are created.

When an editor uploads an image that is not compressed, there are cases (like the carousel in the home page of GPI) where the original image is used.

This is also described at the following stackoverflow discussion:

https://stackoverflow.com/questions/13460188/force-wordpress-to-create-thumbnails-of-same-size-as-the-uploaded-image

We should do one of the following:

a) When an image is added that is smaller than the sizes we use, we should notify the editor that their image is not going to be resized in all the sizes.

or

b) We should rebuild the image (preserving the original), and use the recreted one in the above case.