Definitely overdressed. As a programmer I can say that in general programmers don't dress up nice unless they have a PR job or something. The strictest dresscode I have seen for programmers was work casual, something like this:
https://s-media-cache-ak0.pinimg.com/originals/36/a8/e3/36a8e3ed0e2f7017b78443bb5e9a59b2.jpg
Personally I have to dress decently because I also work as a teacher, but even then I can wear silly shirts because the kids like it. Most programmers I know wear whatever they would wear around the house. We tend to get pretty lax dress codes.
Based on what I have seen from images of Riot employees that seems to be the norm. So long as it isn't profane, or overly sexual and you are wearing shoes it tends to fly.