What i understand from your question is, you want a button on the image. button should be display like it is placed on the image. correct?
If so, you can do that using Absolute position of your control.
<asp:Image ID="Image1" style="position:absolute" runat="server" ImageUrl="~/Water lilies.jpg" />
<asp:Button ID="Button1" runat="server" style="position:absolute" Text="Button" />
Above code is just sample.you need to do some more adjustment and margin with the button control to adjust on desired location. Disadvantage of above resolution is, you can not control on screen resolution. your design will not be looked similar in all monitors with different resolution.
Hope something from above lead you to solution,