The solution to this is a little silly, but it definitely works:
Close Xcode and the interface builder. Now, instead of opening Xcode, then opening the project, go to the project in Finder and double-click on the project. When you open your xib file, the blue file will not detect images that will blink, and then replace them with the correct images, and the drop-down menu will display all your images in the inspector.
source share