add on image

Is a add on image simply a set of extra files made added onto the existing image, (file sets) ie files for a app which
still need to be installed, or can it be a fully functional app, added on in the form of an add on image.
Like a kind of snap shot which would include the reg settings and files in the correct locations.

I also cannot get image explorer to work even after updating java and reading through a number of docs.
Problem in dependency or Java version is not compatible(needs 1.5 or higher)

Log details
Exception in thread "main" java.lang.UnsatisfiedLinkError: no swt-pi-gtk-3235 in java.library.path
at java.lang.ClassLoader.loadLibrary(Unknown Source)
at java.lang.Runtime.loadLibrary0(Unknown Source)
at java.lang.System.loadLibrary(Unknown Source)
at org.eclipse.swt.internal.Library.loadLibrary(Libra ry.java:123)
at org.eclipse.swt.internal.gtk.OS.<clinit>(OS.java:2 2)
at org.eclipse.swt.internal.Converter.wcsToMbcs(Conve rter.java:63)
at org.eclipse.swt.internal.Converter.wcsToMbcs(Conve rter.java:54)
at org.eclipse.swt.widgets.Display.<clinit>(Display.j ava:126)
at com.novell.ImgExplorer.Main.run(Main.java:71)
at com.novell.ImgExplorer.Main.main(Main.java:228)

Thanks
Mark