Mona Lisa with eyes covered with a black bar. This practice fails to prevent the subject being identified. Formerly used in medical publications to hide patient identity, it is no longer considered effective. (Source ICMJE)
In the unlikely event that you don't immediately recognise the subject, just drag and drop it onto Google Image Search and Google will tell you who it is. This shows that if the same or similar images are already online, then attempts to anonymise the image are futile. The Internet never forgets.
/ レオナルド・ダ・ヴィンチ