If you are talking about the menu icon on the device I don't think you can alter the phonegap developer app icon. You need to actually build your app in phonegap build and include your icon files in the res folder like the hello world example. Or you could build your custom version of the phonegap developer app but that would be a lot of trouble just for icons.
Thanks, but I was talking about the icon with "G" in the screenshot, that is referred to the single project in PhoneGap Developer.
If I create a new PhoneGap project instead the "G" icon there is the PhoneGap logo, in this case I have created the project with Cordova and I was asking if there is the possibility to customize the icon that appears in PhoneGap Developer, not the icon that appears after building the app on devices!