It is possible to use Google chart api for icons on a map as described in this blog post. The scale of the icon does work opposed the arcitle in the blog post.
The url to the icon generated by charts in the kml file has to be change from the normal http://chart.apis.google.com/chart to https://www.google.com/chart, because google maps api needs https to retrieve the icons.

{mosmap kml='images/population_2005_charts_pie2.kml'}

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There is however a limit on the number of icons that will be shown on the map with kmlrenderer of Google. If you have more icons than there shown, try to use the kmlrenderer GeoXML.

The kmlrenderer GeoXML has a bug with the sizing or scale of the icons. If you set the iconwidth and -height, the icons will show correctly.

{mosmap kml='images/population_2005_charts_pie4.kml'| kmlrenderer='geoxml'| kmlsidebar='left'| kmlfoldersopen='1'|icon='http://tech.reumer.net/images/demo.png'| iconwidth='32'| iconheight='32'}

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