A few weeks ago I came across with this idea while building some maps in QlikView.
I was switching from bubble (plain shape, no 3D!) to rings style when suddenly realized that we can show two expressions related one to each other (sales vs budget for example) at the same time in a beautiful and useful way.
And, this is the result:
As you can see, the trick is to use 2 scatter charts, one is in the back with the Gmaps image and the filled bubbles showing the Sales.
Then, there is another scatter chart on top with 100% transparent background showing the other expression, Budget in this example. Also, you can use the Background Color property to make it even more clear to see the comparison between the two expressions.
I hope you find it useful and if so, share it!