Or if you want to do like I have done (With no link to upload an avatar), just find this:
PHP:
<if condition="$show['avatar']"><td class="alt2"><a href="member.php?$session[sessionurl]u=$post[userid]"><img src="$post[avatarurl]" $post[avwidth] $post[avheight] alt="<phrase 1="$post[username]">$vbphrase[xs_avatar]</phrase>" border="0" /></a></td></if>
And replace with this:
PHP:
<if condition="$show['avatar']"><td class="alt2"><a href="member.php?$session[sessionurl]u=$post[userid]"><img src="$post[avatarurl]" $post[avwidth] $post[avheight] alt="<phrase 1="$post[username]">$vbphrase[xs_avatar]</phrase>" border="0" /></a></td>
<else />
<if condition="$bbuserinfo[showavatars]">
<td class="alt2"><a href="member.php?$session[sessionurl]u=$post[userid]"><img src="$stylevar[imgdir_misc]/noavatar.gif" $post[avwidth] $post[avheight] alt="<phrase 1="$post[username]">$vbphrase[xs_avatar]</phrase>" border="0" /></a></td>
</if>
</if>
And don't forget to create and upload an image named noavatar.gif to YOURSTYLE/IMAGES/MISC folder.
Here's the one I'm using:
View attachment 13758