If you want to add your own icons or logos to KML-file it makes sense to use styles in the KML file. See this simple sample how to add a marker and a popup text in KML file:
[*osm_map_v3 map_center="47.263,11.395" zoom="15" width="75%" height="300" file_list="../../../../wp-content/uploads/osm_map/My_KML_01.kml"]
You should use relative paths and the icon should have a sice of 32 x 32 pixel saved as transparent png.
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