You should change
Code:
<if condition="$online_userinfo[field6]"><img src="images/clubs/$online_userinfo[field6].gif" border="0" /></if>
to;
Code:
<if condition="$online_userinfo[field6]"><img src="images/clubs/$online_userinfo[field6].gif" alt="$online_userinfo[field6]" border="0" /></if>
That way it'll show up the image name when you hover over it, and it'll be XHTML valid

.