To achieve the desired layout, you will need to use three separate images along with three corresponding divs.
The first div should contain the image for the left side, the second div should hold the central content, and the third div should display the image for the right side.
If you prefer, you can create a button with a similar design using only CSS, eliminating the need for any graphics.
For example:
http://jsfiddle.net/PWNLf/1/
.button{
background: rgb(194,172,224); /* Old browsers */
background: -moz-linear-gradient(top, rgba(194,172,224,1) 0%, rgba(232,241,242,1) 30%, rgba(186,241,244,1) 31%, rgba(18,65,206,1) 100%); /* FF3.6+ */
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,rgba(194,172,224,1)), color-stop(30%,rgba(232,241,242,1)), color-stop(31%,rgba(186,241,244,1)), color-stop(100%,rgba(18,65,206,1))); /* Chrome,Safari4+ */
background: -webkit-linear-gradient(top, rgba(194,172,224,1) 0%,rgba(232,241,242,1) 30%,rgba(186,241,244,1) 31%,rgba(18,65,206,1) 100%); /* Chrome10+,Safari5.1+ */
background: -o-linear-gradient(top, rgba(194,172,224,1) 0%,rgba(232,241,242,1) 30%,rgba(186,241,244,1) 31%,rgba(18,65,206,1) 100%); /* Opera 11.10+ */
background: -ms-linear-gradient(top, rgba(194,172,224,1) 0%,rgba(232,241,242,1) 30%,rgba(186,241,244,1) 31%,rgba(18,65,206,1) 100%); /* IE10+ */
background: linear-gradient(to bottom, rgba(194,172,224,1) 0%,rgba(232,241,242,1) 30%,rgba(186,241,244,1) 31%,rgba(18,65,206,1) 100%); /* W3C */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#c2ace0', endColorstr='#1241ce',GradientType=0 ); /* IE6-9 */
color: #fff;
font-family: helvetica;
padding: 30px 60px;
border-radius: 40px;
text-decoration: none;
border: 1px solid #1241CE;
}