this is my first ios app and when i try to submit it to the app store it gives me the ITMS-90096 error.
I also had a hard time to figure it out. It happened to me after I upgraded XCode into version 7 (iOS 9). Somehow it unassigned launch images and changed Launch Image options with unchecked iPhone Portrait for iOS 6.0 and Prior from the right pane.
After I checked iPhone Portrait it shows assignable iPhone Portrait iOS 5, 6. I just drag & drop images into the proper holders.
Then I archived with this assignment and uploaded binary successfully into app store. I hope this would help.