Erel is incorrect. I had launch images for every single type of device. Firstly, none of them have ever shown on iOS8 in release mode on all 3 devices.
Secondly, Apply randomly choose a device to test, in this case iPad Air. One can only assume that no launch image is ok, but with Apple and with certain devices it is not. I have not seen a working launch image in iOS8 release. I believe they work for most devices. Some of the new ones though, even if you supply the right files, cause the layout to not be drawn at all if the launch is missing.
This is fact. I have 3 devices, all running my layout in release mode with no launch image. It is a rule from Apple you must have one. It is correct that in most circumstances the avoidance of a launch image will not affect your App being accepted HOWEVER it will on CERTAIN devices, like iPad Air the one they told me it failed on. They must now try every device as a new rule. It may be an Apple issue that if no launch image from any manufacturer is available for an "iPad Air" whatever the exact model is, it is a bug in iOS that draws a black screen and never moves on to layout.
I factually saw 3 release apps run my layout before submission. It was rejected because it STUCK on the black screen on an iPad Air. How can anyone work with these variables? So it may not be the avoidance of the launch image, I do agree with Erel and it is factually proven because they didn't come back and say it didn't work on my 3 devices, but I do disagree that there is a systemic issue with SOME devices and whether there is a launch image or not, it gets stuck on black screen.
I maintain and have proven with a skeleton standard app that launch images don't work (show black then go to layout) in B4i in my iPhone 4s, iPad Mini and iPad 4 non retina in my own release mode. This is not what stops Apple, but on newer devices it DOES!