asynchronously load images to a navigation flyout or best way to load images

asynchronously load images to a navigation flyout or best way to load images

I have a Large navigation flyout menu with images displaying the items.
its working fine however the page load time is a little slower since i
have more images to display.
my example code
<ul>
<li>
<a>Cars<a/>
<div class="flyOutMenu">
<img src="img/car1.png" />
<div>Mustang</div>
<div>Honda</div>
<div>BMW</div>
</div>
<li>
</ul>
navigations can have 40 images
any way i can load the image faster via jquery? or handler
Any idea or links would be great thank you.