wp_list_pages with featured image (as background)

hey there,

i’m using

<ul class="item-wrapper"><?php wp_list_pages('title_li=&exclude=17&l' ); ?></ul>

to list all of my pages. and it works fine. but some of the pages have featured images assigned. i already manged how to show the image, but it always appears within a <img>-tag; but what i need is the url of the featured image in order to use it as background-imge of the page-item-container.

is there any chance to do this?

thanks in advance