Those images were not package with JForum, so it's hard to say where they came from and/or if they are licensed.
Try googling for themes. You can use images for PHP-BB themese with some slight modifications.
And you can use just about any images. You just need to make sure the sizes are correct in the syles.css file to match the image (or vice versa).sl.sbc.yahoo.com/ [originally posted on jforum.net by GatorBait3]
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