when I load my application it shows a warning message that
\"Could not load the \"\" image referenced from a nib in the bundle with identifier \"
I have just updated to XCode 9 and it started giving me this issue. I created a new Image Set in the Assets section and added the images I wanted to this, then re-added them to my tab bar images with custom names and it worked fine. Hope this helps!
PROBLEM
This happened to me seemingly out of the blue on a tab bar controller with icons for each tab. The storyboard was still showing my image icons and the assets existed with the expected names.
MY FIX
Select the tab bar icons in their respective view controller and reassign the image like you did the first time.
Based on what @hstdt posted above, it made me think I should check that my image is a filetype that doesn't have any bugs related to it. (https://stackoverflow.com/a/44558948/6804257)
I was using a .gif. I got rid of that image and instead used a .png. Now it works.
My case was a bit different. I was using an old IBDesignable element which had some property of setting an image directly from the storyboard. Since that element was old, hidden and unused the images it had were not present in my assets folder.
Now Xcode won't be able to search this image since it is not in the project anymore. But if you search in the finder, inside your project, you'll find the XIB/Storyboard in which it is mentioned. From there you can find it manually by opening that XIB or Storyboard as source code and search. Once found either replace them with a new image or remove the unused element.