Missing Marketing Icon
According to new guidelines for the XCode 9: we need to drag a new icon with size 1024pt new available icon item named "App Store iOS 1024pt" under AppIcon image set.
IMPORTANT: Make sure to use the icon without Alpha/Transparency
After doing this, the warning will be gone and you should be able to successfully submit the binary to Apple for review.
Reference link: https://help.apple.com/xcode/mac/current/#/dev4b0ebb1bb
Solved by adding iOS Marketing 1024pt icon in project