Changing theme default header & background image

I am trying to replace the default theme header. I have created a new header and background with the same dimensions and name of the theme Blueline. I have uploaded it to the default wp-content/themes/blueline/design/ folder where the images reside, but nothing changes.

The code in the style.css:
#header
{
background-image: url(design/bg.jpg);
background-repeat:repeat-x;
}
.banner
{
background-image: url(design/header.jpg);
background-repeat:no-repeat;
width: 995px;
height: 216px;

What am I doing wrong??
http://prop4lease.com/