Speeding up Page Loads for Image Background

Working Environment: I have a website that must have an image background (pretend its a math problem and there is no choice but to accept this).

Is there a way for me to format my html and CSS so that background loads faster?

One Idea I had was instead of having the "body" carry the image background, to instead partition the site into rows (using the tag) in the hopes the browser will load the divs, hence it can present some of the visible portions of the site before having loaded EVERYTHING.

I'm pretty sure my method of manual div seperation (And setting backgrounds of each slice) isn't the the most efficient approach to this. What is the best way to carry out this technique?