There is a a way to add "Overlays"
This can be any TileSource, an existing one or a new one you create your self.
I also have a basic TileSource class for WMS EPSG:3395 / EPSG:900913 which is the same kind of projection like DeepEarth uses
the WMS TileSource in the download is WMS EPSG:4326, which is not the same projection so the map distorts
Also I have a basic TileSource class for ArcGIS server as well
I will post these up some here in next couple days after I clean them up a little bit if anyone would like to check them out.