From eclipse, this runs fine and returns the icon. I don't reach "past new icon" when I am executing the jar file, and the imageURL is null.
My class is in "durz.images"; I tried it once with the images in that same directory and just specifying iconName; I tried moving the images to their own "images" subdirectory and specifying "images/" + iconName.
I have verified that the jar file contains the images in the directory path, relative to the root of the jar file, that they're supposed to be in. I did that once when they were in the same directory as the class, and again after I moved them to their own images directory off the directory the class was in.
I am aware that the "/" at the front of the getResource() string parameter means "absolute path within the jar", and without the "/" the path is relative to the path the class is in, in the jar.
SSCE helps again; I'm on Windows, and in eclipse, case is not significant on the resource file. It is significant, however, in the jar. So the case of the resource filename must be the same as stored in the jar.