For iOS, Corona SDK uses the Apple Maps SDK.
For Android devices we use Google Maps.
In both cases, a “native” object is returned. Native objects exist on a layer above OpenGL where Corona’s other drawing features exists. It is not possible with Corona SDK to create sprites or images on top of the map.
We do support adding of pins (with or without custom images) on to the map and an info bubble that shows when a pin is tapped.
That is the limit of what you can do with our built in mapping (which is still pretty useful!).
If you want to do more with maps, I would suggest considering using Google Maps through a webView. You still can’t get Corona SDK to draw on top of it, but you do have access to many of the Google Map API features for drawing lines, polygons and such over a map. I built a weather app for my wife and overlaid Weather Underground animated GIF tiles on top of the Google map and gave her pinch-zoom-scrollable weather radar.
Rob