As said there just need to find any location you want to change the avatar to Large (which is 192x192) and change it. Then requires some adjustments to other properties to compensate. You can do the change to large and then actually make it a bit smaller like you want as well but it would require me getting off my lazy butt.
That tutorial will also allow for aspect ratio correct avatars. I believe it is a little dated as I made my own adjustments after learning the trick.