Attributes for list item background images

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I have a JQuery slider on my home page and the basic HTML looks like this...

<div id="slider">
<div class="flexslider">
<ul class="slides">
<li class="slide-1"></li>
<li class="slide-2"></li>
</ul>
</div>
<div class="headline">Respect <span>|</span> Responsibility <span>|</span> Excellence</div>
</div>

.slide-1 and .slide-2 both specify images in the background which work well. I'm having trouble building a custom block for this and I am looking for a way to use custom attributes to add classes to list items and then be able to add images in page properties or similar.

Is this possible?

I use 'Designer content' but it will only let me add images into the div.

dhdesign