I have been playing around with various map plugins for word press, and the ONLY one that worked immediately (without any issues) was the “Basic Google Maps Placemarks” plugin.
The thing I loved about this plugin, is that you could categorise the Placemarks into various sections. That made my life very easy. In addition to this, you can also change what the Placemark displays like. For HL Training, we wanted to change the usual Placemark to display as a forklift. This is easily achieved, simply by going to the Placemark and scroll down the right hand menu. You will see the “Featured Images” – just upload an image there, and you will notice that the image now displays on the map.
The only issue with this is, that you have to do the featured image for EVERY Placemark.