Adding PIcture to Solon Theme Header

I have been searching around some blogs to add a picture to the theme header.

This is the basic CSS I have found, but can’t seem to get a picture to work

Do I need to make adjustments to the pic for size?

any suggestions would be great

Bret

webstie: snowstrength.com

CSS;
#header {
width:660px;
margin:0 auto 10px;
border:1px solid #ccc;
background: #fff url(https://snowstrength.com/wp-content/uploads/2014/07/kane-and-jaketest.jpg) no-repeat top right;
}