Well easiest way is to create a new field
remember the fieldid (let's guess it is five)
and then add this:
PHP Code:
<if condition="$post['field5'] !=''">
<a href="http://bitwine.com/advisors/$post['field5']"><img src="the_bitwine.gif"></a><br /></if>
or what ever the correct link should look like
(to prevent misuse, it's better to use PCRE (regular expressions)

)
to postbit AND postbit_legacy somewhere below the avatar... like
after:
PHP Code:
$vbphrase[posts]: $post[posts]
or to get closer to aim/skypeicons find this
PHP Code:
<div>$post[icqicon] $post[aimicon] $post[msnicon] $post[yahooicon] $post[skypeicon]</div>
and make it
PHP Code:
<div>$post[icqicon] $post[aimicon] $post[msnicon] $post[yahooicon] $post[skypeicon] <if condition="$post['field5'] !=''"><a href="http://bitwine.com/advisors/$post['field5']"><img src="the_bitwine.gif"></a></if></div>
'sid