Example with ShowCheckBox property enabled <i386:ImageCheckBox id="ImageCheckbox1" runat="server" ImageChecked="images/yes.gif" ImageUnchecked="images/yes.gif" ShowCheckBox="true" />
Example with AutoPostBack <i386:ImageCheckBox id="ImageCheckbox2" runat="server" ImageChecked="images/yes.gif" ImageUnchecked="images/yes.gif" AutoPostBack="true" />