If the images don't need to be edited then you can put them in your JAR instead.
I usually use NetBeans but I have Eclipse as well so I'll try to guide you through doing this. First make a folder in the root of your project where you want to store your images, if you don't already have one, and put the images in it. I'd use 'res' or 'img' as the name to make your intent clear.
Next open Eclipse and right click on the project, go to 'Java Build Path' and click on 'Add Folder', find and select the folder you used in the previous step. You should now see this next to 'src' in Eclipse. Anything in here will now be put in your JAR.
You will probably need to change the code to load these images. Something like:
Should do this for you, this gets you an InputStream. Note the slash, you will need it. Or maybe:
Which gets a URL.
Hope this helps!