Assalam aliekum
The fact that 1 person could sit and make 100,000 signatures (hypothetically) is just one of the reasons why online petitions basically mean nothing to anyone except the people who are supporting the cause truthfully and honestly.
Even real pen-and-paper petition are difficult to get action; petitions are just that - petitions. Petitions are requests; they are not requirements and no one is required to act on the nature of a petition. If we get 500,000 signatures and they don't remove it, what is going to happen? Nothing, except, insha'Allah, people would stop going to that particular site.
That's why I asked - did WIKIPEDIA itself actually SAY it would remove the pictures if 100,000 signatures were obtained? Or did the person who made the petition say that?
I am not trying to be difficult, but we must always be realistic. Pen-and-paper petitions are more influential because the people BEING petitioned can actually (and more easily) check to see if these are real people and if they really signed the petition. Online petitions are almost impossible to check, thereby making them even less effective than the marginally effective paper petitions.