I wrote a script that auto generates icons for cordova using ImageMagick:
https://github.com/AlexDisler/cordova-icon
To use it, create an “icon.png” file and place it in the root folder of your project, then run:
cordova-icon
and it will generate all the required icons for the platforms your project has.
You can also configure it as a hook in your cordova project so the icons will be generated every time you build the project based on the icon.png you’ve added. (instructions in the readme).