ImageEditor is a good free image editing program written in java.
I had the need for an image editing software capable of working with PNG images, with layers, and working in eCS. Pixel unfortunately is very buggy and way behind the major platforms. The other image editing programs aren't capable of working with PNG images or are very simple and don't support layers.
So I went looking for Java packages and found ImageEditor which unfortuntely required java 1.5. I sent a message to its author, and after a few hours he had removed java 1.5 dependencies and uploaded a new package compatible with our limited choice of JREs!!!
You can see it and download it here: http://www.jhlabs.com/ie/.
If you like the package please send your thanks to the author.