It doesn’t really say anything about RotMG as a whole, as there are only very few pictures when you compare it to the total amount of players.
It could also be that there are simply more white players who are willing to show a picture of themselves on these forums.
With such a small group, there is very little you can say, and even if that wasn’t a problem, there are other possible causes for the percentage of white players being seen in this thread.