[pein87]

there already is one shown its the unknown.gif image in the misc folder in the main images folder. All you have to do is change it out with another avatar image named unknown.gif

or like said above look in post bit and find

the if conditional that displays the avatar and replace with this.

<if condition="$show[avatar]">
<if condition="$vbulletin->userinfo[hascustomavatar]">
<img src="image.php?u=$bbuserinfo[userid]&amp;dateline=" alt="$bbuserinfo[username]'s avatar" />
<else />
<!-- add path to your own image -->
<img scr="" alt="" />
<!-- /add path to your own image -->
</if>
</if>

I use somthing similar for my avatar on nav bar mod. Hope this helps you.