I often have need to see if I can find the original source, rights and permissions for images I find on the internet. Contrary to too common practice you really cannot just use an image freely because you found it on the internet. Rights are probably still owned by the person that created it and their may be model rights involved too. Get caught using an image for commercial purposes without rights assignments and you could be looking at paying a hefty damages settlement.
Anyhow, check out TinEye (beta still) for reverse image search. Just upload the image and it races off to find its other appearances and hopefully the original source.