I found LaunchImage in Images.xcassets. I inserted my png file and it worked fine. Then I updated it and it is not shown again. Only a white screen appeared. I removed it completely, inserted it again. Does not help. The recomendation for portrait is 1242x2208. So I created exacly this size. No change. Where is the problem?
Did you try to use the LaunchScreen.xib as a launch screen?
Check out my answer to this question because you may have a similar issue: Landscape Launch Images on Xcode 7 madness - [FIXED]