[flup]

You can add specific text/images/code to your users signatures before or after their own signature. You need to edit postbit and/or postbit_legacy to do so. I think somewhere in the middle or a little more down to the bottom it says something like

_____________<br />
$userinfo[signature]

or something.. you can add the code before or after the $userinfo variable.

Be sure to also remove the <condition if="$userinfo[signature]"> code, so that it is showed by default without the user having anything in his signature.

I use this aswell to link to specifc parts of my forums.