iOS guidelines ask us to package 768 x 1004 (portrait launch image) or 1024 x 748 (landscape launch image) sized launch images for iPad irrespective of the fact whether the app is fullscreen or not. However if we intend to extend the duration of our full screen by showing the same launch image for some more time so that we can do the initialization in the backend, we tend to see a small drift (the launch image shown by us shifts by a small amount).
This is because of the fact that scaling used by iOS to show the non fullscreen image is different from what when we display the image.
Can someone help me fix this?
I've seen that Apple document that requests Default.png files of 1024x748 and 1004x768. However, if your app specifies that it's a full screen app (status bar hidden), then I think it's ok to make your Default.png files (for iPad) the full 1024x768, which makes this problem go away.
I'm just looking at a full screen universal app I have now, that has been released, and its launch image is full screen (1024x768).
Running in the simulator works just fine (and I marked up the image to make absolutely certain that it wasn't cropping off the top 20x and then rescaling).
I don't have an iTunes Connect app that I can currently validate against (easily), so it's possible that it'll complain upon submission to iTunes Connect. But, I doubt it.
If you look at the project Summary tab -> iPad Deployment Info, it will show a warning for your Launch Image sizes:
So, I take that as a recommendation, not a requirement.
Edit: also, see this other stack overflow question. That answer also suggests using 1024x768 images, and it hasn't received any pushback from the community (after 19 months+)