If you're looking for icon images, they are in \mod\profile\graphics folder (unless you're using a theme).  Try to remember last thing you did (changed the code, etc.). Your code to display latest members probably specifies size like this:

elgg_view("profile/icon",array('entity' => $user, 'size' => 'small'))

Hope this helps.

I want the icons/avatar sizes to be the same. Right now, I have 40X40 mixed up with 60x60. Any help?

Did you change the size at some point?

yes, I did something a while ago but I don't remember the files. I know there were 2 of them.

You would need to write a script that processes all users and resets their icons to your new size. Alternatively, you could do it in the browser by setting the width and height in the html.