How to install..
Go to CP ---> Design (templates) ---> Forum --> Appeareance of entries
Find this :
Code
<img alt="" title="$USERNAME$" class="userAvatar" border="0" src="$AVATAR_URL$">
And replace it with this:
Code
<img alt="" title="$USERNAME$" class="userAvatar" style=" width: 100px; height: 100px; border: 8px solid #333333;margin-bottom: 4px;" src="$AVATAR_URL$">