Can I just remove the template, or is there a better way of doing it?
The replies conclude by just removing it from the templates. Is there another better way of doing it, or is that the best way?
^ that is the best method - however needs to be done for all the themes.
And MyBB 1.8.x has no avatar gallery (however a plugin is available for the interested)
You can delete all avatars just to be sure no-one will bypass it.