in css/home.css
edit the background-image property of the storeMessage selector to change that image to your own:
#storeMessage {
background-image: url("../Images/storeMessage_bg.png");
background-repeat: no-repeat;
height: 260px;
margin-left: 1px;
overflow:hidden;
background-color: #06245c;
margin-right: 1px;
}