Header Image problem :( :(

I have followed the steps in the FAQ's "How do I change the Header Image?" article, precisely.

But my change still has no effect.

(I am using a custom template which i also set up following directions from the FAQ.)

What could i be missing??
Please help.

I just want to make it clear that i do have a jpeg file for the image

it's called nye10head.jpg

and it is in the directory includes/templates/nye2010/images.

I have added the following code to the file includes/templates/nye2010/css/stylesheet.css:

#logoWrapper {
width:760px;
height:110px;
background-image:url(../images/nye10head.jpg);
background-repeat:no-repeat;
}

my template directory looks like this

/includes/templates/nye2010/
/common
/css
CSS_read_me.txt
print_stylesheet.css
stylesheet.css
stylesheet_css_buttons.css
/images
nye10head.jpg
/sideboxes
/templates
template_info.php


what can i be missing.

i am really at a loss for ideas here.
any help would be greatly appreaciated.