#floating-form {
 background-image: url('http://ici adresse de votre image');
 background-repeat: repeat;
 background-position: 50% 50%; 
 margin-bottom: 100px;
 right: 10px;
 /* coins arrondis */
 -moz-border-radius: 10px;
 -webkit-border-radius: 10px;
 -khtml-border-radius: 10px;
 border-radius: 10px;
/* bordures ombrées */
 -webkit-box-shadow: 2px 4px 12px #666;
 -moz-box-shadow: 2px 4px 12px #666;
 box-shadow: 2px 4px 12px #666;
 filter:progid:DXImageTransform.Microsoft.Shadow(color='#aaaaaa', Direction=135, Strength=12);