Background images to create different textures across the page

Hi:

I'd like to add background images to different sections of the website, like they do here: taylorswift.com.

I'd like if someone could explain me where to start, as my attempts didn't look good, because I'm not sure what sections to target so the image sometimes show, sometimes doesn't.

For example: I've created a div background-intro below the introductory paragraph in the homepage, but if I place an image there it doesn't show.

Another example is that if I want to target the footer, for the image to cover all of it I have to write:

#footer {
background: #ebebeb url(light-blue-wall-2.png) repeat;
}

#footer .inside {
background: #ebebeb url(light-blue-wall-2.png) repeat;
}

#footer .inside .footer .ce_text {
background: #ebebeb url(light-blue-wall-2.png) repeat;
}

Is there a way where I can write something more efficient?

Ah! Here's the website: assembly21.com

Thanks!