This seems to be a bug in the phonegap cli. If you are using phonegap local build, the icons and startup images should be copied manually to the phonegap/platforms/<platform>/res/drawable-<res>
folder. Look at the bug here https://github.com/phonegap/phonegap-cli/issues/58.
I have copied my icons to the respective folder and the build is having the right icons.
If you are using the phonegap cloud build, this will work out of the box.