Seems like as guided by @kleopatra, this surely is the right way.
When you create resources folder, make sure you do it by right clicking your project, then go to source folder and name it as resources/icons and then manually put your images in that folder, and go back to your eclipse and refresh your project. Now you can use these images in your runnable jar also.
Now in order to use your image/icon in your Classes use this
private ImageIcon getImage(String path)
{
URL url = getClass().getResource(path);
System.out.println(url);
if (url != null)
return (new ImageIcon(url));
return null;
}
Here your path
will be the name of the image
prefix it by a forward slash, which is inside your resources/icons
folder like "/myIcon.png"
I wanted to be sure, before i post my answer, so tested it.
Else give me some time, I will put all steps somewhere for you to see.
More info related to the whole thingy can be found on this another answer of mine :
Load ImageIcon Exception