I know this is not the answer you want to hear - but you cannot pass any image via link_to_route.
The problem is the output from the HTML class is escaped automatically. So if you try to pass this:
{{ HTML::link_to_route('author','<img src="'.URL::base().'assets/images/image.jpg" alt="icon" />')) }}
it comes out like this:
<img src="http://laravel3.dev/assets/images/image.jpg" alt="icon" />
which will just be text on the screen - no image. Instead you need to use URI::to_route('author')
and generate the link yourself. So make a helper a like this (not tested):
function link_to_route_image($route, $image)
{
$m = '<a href="'.URL::to_route($route).'">'
. '<img>'.$image.'</img>'
. '</a>';
return $m;
}