I am not sure I understand your question - what to make work with sprite.gif? If you create a custom RadCalendar skin, based on some of our embedded skins, it will have a sprite image, which should work as expected, because the CSS file will contain all the necessary background position styles. In this case you don't need to set ImagesPath.
Please explain what exactly are you trying to do, what is the RadControls version and what custom skin you have (how have you created it).
the Telerik team