Hello!

I just downloaded your image 2 and plopped it onto an alpha plane in a new scene (choose "add alpha plane" and then add the image as color and the inverted image as alpha in the following dialog window). Seems to work as you intended with the default settings. I can see many small drops. Mapping is set to "Automatic". No adjustments to scale or any other parameter were necessary. Can you show a screen shot of your set up and the material tabs for the alpha plane.

Make sure that the alpha plane is far enough away from the camera to show more than a small section.

Ciao
TD