Assuming you're working on windows, this is actually due to gif images
not being converted on windows. If you change to another image type it
should work, see below.
<div style="float:left;color:#00FF00;background:url('http://
www.pdftron.com/assets/images/carousel/header_mob1.png') repeat scroll
0 0 ">
<p>And he was clad in coat and hood of green. A sheaf of peacock
arrows bright and keen</p>
</div>
We aim to have HTML2PDF gif conversion working on windows in time for
the next regular release of PDFNet.