This is normal. The thumbnail created after submitting your photo to your online application file is automatically created by our system as a small square image with rounded corners. Therefore, if your original image is not square (which is very common), the thumbnail generated by the system will only show part of the original image.
However, this is not important as these thumbnails are only used as an indication of what photos have been placed in your file.
In all cases, the jury will only examine the original photographs submitted in your application.