Insertion image en back-ground dans un fichier PDF généré parHTML2PDF

<style type="text/css">
	table {
		width: 100%;
		color: #717375;
		font-family: helvetica;
		line-height: 5mm;
		border-collapse: collapse;
	}
	h2  { margin: 0; padding: 0; text-align: center; }
	h3  { text-align: center; line-height: 7mm; }
	h4  { text-align: center; }
	h5  { text-align: center; }
	
	p { margin: 5px; text-align:left; }
	
	.border th {
		border: 1px solid #000;
		/*border: 1px solid #000;*/
		color: white;
		background: #333;
		/*background: #000;*/
		padding: 5px;
		font-weight: normal;
		font-size: 12px;
		/*font-size: 14px;*/
		font-weight: bold;
		text-align: center; 
	}
	.border td {
		border: 0px solid #CFD1D2;
		padding: 5px 10px;
		text-align: left;
		/*text-align: center;*/
	}
	.cadre_rouge {
		border: 1px solid #000;
		/* border: 1px solid red;*/
	}
	.data {
		border: 1px solid #000;
	}
	.no-border {
		border-right: 1px solid #CFD1D2;
		border-left: none;
		border-top: none;
		border-bottom: none;
	}
	.space { padding-top: 250px; }
	
	.1p { width: 1%; }   .2p { width: 2%; }
	.3p { width: 3%; }   .4p { width: 4%; }
	.5p { width: 5%; }   .6p { width: 6%; }
	.10p { width: 10%; } .15p { width: 15%; }
	.25p { width: 25%; } .30p { width: 30%; }
	.33p { width: 33%; } .35p { width: 35%; }
	.40p { width: 40%; } .50p { width: 50%; }
	.60p { width: 60%; } .65p { width: 65%; }
	.75p { width: 75%; } .80p { width: 80%; }
	
	.text_footer { font-family:helvetica; font-weight:normal; font-style:normal; color:#717375; text-align:left; }
	.text_footer2 { font-family:helvetica; font-weight:normal; font-style:normal; color:#717375; text-align:left; }
	
	.hr_style { color: #999; }
</style>

<page backtop="10mm" backleft="10mm" backright="10mm" backbottom="10mm" footer="page;">

	
	<page_header>
		<table style="margin:auto; margin-top:5px;">
			<tr>			                    
				<td><img src="drapeau.png" width="80" /></td>
				<!--
				<td class="60p">
					<h3>SOCIETE</h3>
				</td>
				-->
				<td><img src="logo.png" width="120" /></td>
			</tr>			
		</table>
		<!--<hr />-->
	</page_header>
	
	<page_footer>
		<hr class="hr_style" align="center" />
		<table align="center">			
			<tr>			                    
				<td class="text_footer2" align="center">Jordan LEFEBRE <br>Directeur Général</td>
				<td class="2p"></td>
				<!--<td align="center"><br />4785 Av. Géné De Gaulle</td>-->
				<td class="1p"></td>
				<td class="text_footer2" align="right">
					<img src="upload/client/<?php echo html_entity_decode($attestation['logo_client']); ?>" style="width:50px;" /> 
					 <img src="logo-2.png" width="50" />
				</td>
			</tr>
			<tr>			                    
				<td class="text_footer2" align="left">www.******.com</td>				
			</tr>
		</table>
	</page_footer>
	
	<div style="height:auto; border:2px solid#09F;" class="">
		<table style="margin-top: 100px;" align="center" class="">
			<tr>
				<td class="65p"><h2>ATTESTATION DE FIN DE FORMATION</h2></td>
			</tr>		
			<tr>
				<td class="65p"><h5>Cette attestation indique que</h5></td>
			</tr>
			<tr>
				<td class="65p"><h4><?php echo html_entity_decode($attestation['nom_stagiaire'].' '.$attestation['prenom1_stagiaire']); ?>  (ID : <?php print_r($_GET['imprimer']); ?>)</h4></td>
			</tr>
			<tr>
				<td class="65p"><h4>Né(e) le <?php echo html_entity_decode($attestation['datenaiss_stg']); ?>, <?php echo html_entity_decode($attestation['paysorigine_stg']); ?></h4></td>
			</tr>
			<tr>
				<td class="65p"><h5>a suivi avec succès la formation (has satisfactorily completed the following course)</h5></td>
			</tr>
			<tr>
				<td class="65p"><h3><?php echo html_entity_decode($attestation['lib_formation']); ?></h3></td>
			</tr>
			<tr>
				<td class="65p"><h5>En date du: <?php echo html_entity_decode($attestation['ddebut_session']); ?><br>
				Valable jusqu'au: <?php echo html_entity_decode($attestation['ddebut_session']); ?></h5></td>
			</tr>
			<tr>
				<td class="65p">
					<h5>Client: <?php echo html_entity_decode($attestation['nom_client']); ?> [ Code client: <?php echo html_entity_decode($attestation['code_client']); ?> :: 
					Commande: <?php echo html_entity_decode($attestation['code_cmd']); ?> ] <br>Stage comprenant les modules suivants: 
					 <br><?php echo html_entity_decode($attestation['lib_module']); ?></h5>
				</td>
			</tr>
			
		</table>
	</div>
	
</page>