If you want to check whether the image is uploaded or not,
You can check the ‘hascontent’ attribute, if it is true then the image is uploaded
Hope it helps!!
Depends on how is your entity which is a specialization of Image.
Now if your scenario was with 1 image uploading at a time then, $documentUpload/HasContents
but if you have multiple images then you need to loop/iterate through this image list then individually find out if $documentUpload/HasContents is true or not.