You can remove the asp:Button's default background and borders and apply a custom background image. However, this question does not seem to be related to RadControls.
<asp:Button ID="Button1" runat="server" Text=" "
style="width:128px;height:86px;border:0;cursor:pointer;background:transparent no-repeat url(http://www.kaleidacare.com/images/foster-home-software.jpg);" />
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