It can matter to some people, especially because, at least from personal experience, I've found characters using anime profiles often lack a certain... realism. I'm guessing this RP will be a bit more grounded than, for example, Naruto. It's not going to be much like an archetypical anime, so having anime-styled characters could be distracting at best.

There's nothing inherently wrong with anime character images, but sometimes tonally, they just don't match, like in here.