The way I used to do this with phone gap (in the config file) no longer works, and I see that the image that I imported into C3>icons>loading-logo.png is being used as the CVDLauchscreen.storyboard file in the XCODE project, which is being used as the launchscreen. In XCODE I did load my splash screen images (all the required sizes) in images.xcassets, but they're not used for some reason (?).
The problem with using the loading-logo.png is that it is tiny and looks really unprofessional on an iPad.