My Suggestion is an abuse function on each viewer-version.
So if a visitor thinks this image is not reasonable, he clicks on the Abuse-Button.
Each image can have (for example) 20 abuses (20 abuses overall/in a week etc.), if the limit is reached the image is blocked/deleted or something else.
If the image gets blocked by reaching the abuse-limit the admin could have the opportunity (in the admin area) to delete/reactivate the image.
So if a visitor thinks this image is not reasonable, he clicks on the Abuse-Button.
Each image can have (for example) 20 abuses (20 abuses overall/in a week etc.), if the limit is reached the image is blocked/deleted or something else.
If the image gets blocked by reaching the abuse-limit the admin could have the opportunity (in the admin area) to delete/reactivate the image.