Code:
<if condition="$show['avatar']">
<a href="member.php?$session[sessionurl]u=$post[userid]"><img src="$post[avatarurl]" $post[avwidth] $post[avheight] alt="<phrase 1="$post[username]">$vbphrase[xs_avatar]</phrase>" border="0" class="whiteborder" /></a>
<else />
<!-- Default Avatar -->
<a href="member.php?$session[sessionurl]u=$post[userid]"><img src="images/styles/seogreen/misc/noavatar.gif" alt="<phrase 1="$post[username]">$vbphrase[xs_avatar]</phrase>" border="0" class="whiteborder" /></a>
</if>
Edit the image path under default avatar