Registering variables via plugin?

[HMBeaty]

For vBulletin 4+

Not sure if this can be done or not, but is it possible to register variables via a plugin? Or maybe there's something I'm missing in my code. This is the code I'm using atm:

PHP Code:

$fbimg = $vbulletin->options['usml_navnet_fbimg'];
$twitterimg = $vbulletin->options['usml_navnet_twitterimage'];
$rssimg = $vbulletin->options['usml_navnet_rssimage'];
$skypeimg = $vbulletin->options['usml_navnet_skypeimage'];
$ytimg = $vbulletin->options['usml_navnet_ytimage'];

$template_hook['navtab_end'] .= '
<a target="_blank" href="mysite1.com"><img style="margin:-2px 4px 6px 10px" src="/{vb:raw fbimg}" alt="" /></a>
<a target="_blank" href="mysite2.com"><img style="margin:-2px 4px 0 0" src="/{vb:raw twitterimg}" alt="" /></a>
<a target="_blank" href="mysite3.com"><img style="margin:-2px 4px 9px 0" src="/{vb:raw rssimg}" alt="" /></a>
<a target="_blank" href="mysite4.com"><img style="margin:-2px 4px 0 0" src="/{vb:raw skypeimg}" alt="" /></a>
<a target="_blank" href="mysite5.com"><img style="margin:-2px 4px 4px 0" src="/{vb:raw ytimg}" alt="" /></a>'; 


But the images aren't showing. The links are there, but no images. So I'm guessing $fbimg, $twitterimg, $rssimg, $skypeimg and $ytimg still need to be registered in order for them to show...