I would like to plot radio towers on a map. How could I place a jpg instead of a dot on a lat/long on a location on a map?
Not sure you can do that in simple XML.You will have to create custom map layers using something like leafletjs. Or you can try this app
http://docs.splunk.com/Documentation/CustomViz/1.0.0/RealTimeLocation/RealTimeTrackerIntro