Background derriere 1 champ de formulaire

<form action="admin/includes/contact/contactf.php" method="post">
     <p class="petit">
		<label for="name">NOM:</label>
		<input type="text" id="name" name="name" size="26"/>
	</p>
		<p class="petit">
		<label for="email">COURRIEL:</label>
		<input type="text" id="email" name="email" />
	</p></br>
	<p class="grand">
		<label for="infos">MESSAGE:</br></label></br>
		<textarea id="infos" name="infos" rows="5" cols="30"></textarea>
	</p>
		<INPUT name=Send type=image value="Send" src="pics/envoyer.png" alt="Send">
</form>

.petit
{
background: url("pics/petit.png");
}