Дык!
<span style="background: url('https://yastatic.net/morda-logo/i/citylogos/yandex_no1-logo-ru.png');"></span>
<script type='text/javascript'>
var o=document.getElementsByTagName('span')[0];
val="background: url('{{ asset('layers/'. $template_folder .'/img/' yandex_no1-logo-ru.png') }}');";
o.setAttribute('style',val);
</script>
Вот в консоли получается
<span style="background: url('{{ asset('layers/'. $template_folder .'/img/' yandex_no1-logo-ru.png') }}');"></span>