in admin/functions.php
find:
if ($post[avatarid]!=0) {
$avatarurl=$post[avatarpath];
} else {
if ($post[hascustomavatar] and $avatarenabled) {
$avatarurl="avatar.php?userid=$post[userid]&dateline=$post[avatardateline]";
} else {
$avatarurl="";
}
}
comment that out and put:
if ((file_exists("$userinfo[username].gif ")==1) && $avatarenabled) {
$avatarurl="$userinfo[username].gif";
} else {
$avatarurl="";
}
}
you should then not have to make any template changes at all from the original to display this avatar instead. remember to get rid of the !($bbuserinfo[showavatars]) bit on the line below it if you havent tied this system in with the users showavatar variable. forgive any errors... been up for 2 days with a busted jaw
hope that helps