When I use the Public API to create a content of any kind of content object with an Image attribute, I can't have the image displayed in the frontend or in the admin interface.
To create content with the API, QA is using the CreateImageCommand.php given in the API cookbook.
When troubleshooting the issue, I found out that the image binary file was stored in a location similar to:

ezpublish_legacy/var/ezdemo_site/storage/images/1/2/3/0/321-1-eng-GB/ValidJpgImage.jpg

If I use the legacy admin interface, the image is correctly pubished and displayed, and stored in a location similar to:

ezpublish_legacy/var/ezdemo_site/storage/images/folder26698/valid-jpg-image/321-1-eng-GB/Valid-JPG-Image.jpg

This was discovered while testing EZP-26963.