Your options are a custom control or use the style BS_OWNERDRAW. In both instances you will have to handle the display yourself as a standard button does not have this capacity. It is most probably best to do this using a bitmap for the button.
Any non standard looking button can be drawn using a bitmap. Use BS_BITMAP as the style, get rectangle coord for the button window, CreateCompatableDC, CreateCompatableBitmap, BitBlt image, ExtTextOut text string, then, DeleteDC the compatable DC, finally BM_SETIMAGE using button handle and memory compatible bitmap handle. Wala! you can draw anything thing you like.