The detailed
review could involve contacting the copyright holder.
unfortunately the structure
of present copyright laws and also the lack of any decent mechanisms for searching the net
for copies of images (i think google images only supports searching for text) make it
impossible to tell for sure who the real copyright holder of an image is.
you can contact the person who the uploader claims is the copyright holder but if the
uploader claims they made it themselves you can never be sure if they are telling the
truth.