Update: PhoneGap Build is no longer maintained by Adobe. We recommend VoltBuilder instead, that we use ourselves. VoltBuilder can create the image assets and publish to App Store and Google Play during the build, so great stuff.
The information below can mostly also be applied to VoltBuilder and similar tools, but VoltBuilder has its own basic template.
This tutorial is for first-time users as well as those that want to switch to using PhoneGap Build instead of the command-line tools.
Please send feedback about the tutorial and template via the form on the home page. Other questions should be posted at the PhoneGap Build community.
You can use Abiro Cordova Image to create all the different sizes of icons and splash screens needed for projects. The tutorial is continuously kept in sync with that tool.