adding background image to title

Hello. this is my website:
https://1linkgames.co.cc/
as you can see i’m using weaver II theme, and there is no header background image option there.
all i could do is to add my desire image to the title image.

i want the image to be under the title, but i cant do that.
i tryed adding
“<style type=”text/css”>
html, body, div, span, iframe, wrap
{
background-image:url(‘https://1linkgames.co.cc/wp-content/uploads/2012/07/2.jpg&#8217;);
border: 0;
margin: 0;
outline: 0;
padding: 0;
vertical-align: baseline;
}
</style>”
to the header-raw.php but it does nothing, and when i add this to the header.php it got all screwd up, the picture is cut and shown in many places.

is the code i wrote the right code to add to make header background?
if yes, where should i add it?

Thank you very much