Hello Tim!
I am glad to inform you that I coped with this task.
I keep my plain file where I list names of 50 images in separate folder called domain2/lib/JavaHelp/other where I also keep all uploaded photos.
It is outside my deployed project.
domain2/lib/JavaHelp/other is virtual directory which I registered on glassfish very easily as described at
http://www.marceble.com/2009/07/virtual-directories-in-glassfish/
Then I read data from url by this piece of code:
Isn't it great approach?