The ASPxPopupControl supports the Transparency feature, which means you can create custom-shaped popup windows. For this purpose, set the control's BackColor property to 'Transparent' and provide the appropriate background image.
In this demo, puzzle elements are represented by ASPxPopupControl instances. Each puzzle element's shape is defined by a specific partially transparent .png image, which is set as the background image of the corresponding popup control (via the control's BackgroundImage property). The BackColor property of each popup control is set to 'Transparent'. To allow popup windows to be dragged, the AllowDragging property is set to true and the DragElement property is set to Window, for each popup control.