Changing header background

Hey

I wanna change the header background, this bit to be exact:

View post on imgur.com

I have tried to add this into the CSS(via the customizr theme Custom CSS place)

header.tc-header {
/* Adjust the Image location ‘wp-content/uploads/NAMEOFFILE.png’ */
background: url(url to my file here) repeat 0 0;
}

but it still does not work. I have checked to see that the url works and tried to change the edit parameters but nothing works.

Thanks