I was thinking at first, why does CB connector link the large CB Image instead of the small one from CB to the forum? I know I could edit CB connector, but controlling the large one is nice depending on the forum layout. With that being said i used CSS to control the forum avatar.
In forum/templates/subSilver/overall_header.tpl
Around Line 143 find:
[code:1].postdetails { font-size : {T_FONTSIZE1}px; color : {T_BODY_TEXT}; }[/code:1]
and add this code after
[code:1].postdetails img {max-width: 125px; width:expression(this.width > 125 ? "125px" : this.width); }[/code:1]
so basical, max-width: 125px controls the width in firefox
the next controls in ie6
image greater than 125 size down to 125. you can replace with whatever you want.