I think your current icons might be a little too complex. Think about ways to simplify them.
Your best bet might be to use color and number similar to the way the diagram Yallow showed.
But each color related to one of the twelve types.
So places you had just one it would show the icon and places where there were more it would show the color and number.
I think I wouldn't use solid color as this might be overpowering but a mix of a colored circle with a white fill might work.
download bmml source – Wireframes created with Balsamiq Mockups
Had a few more thoughts on this...
If you are using color you might want to de-emphasize the color on the map... a grey scale or slightly muted map might work better.
Also I was thinking that 12 sorts of elements was a lot. There must be some that are more key than others. Why not only show the top five and hide the others in an "advanced" or "more" setting.
Will stop thinking about this now!
download bmml source