There are some here: http://help.editboard.com/Miscellaneous-c2/Design-for-forums-Self-service-f6/Gallery-f9.htm

And one created by eon: online here: http://help.editboard.com/Miscellaneous-c2/Design-for-forums-Self-service-f6/Proposal-f8/Grass-Green-By-Eon-Online-World-25-DoneUpdated-26-07-t2213.htm

You can do a google search for: free phbb themes

This is the best site for phbb themes I found: http://www.phpbb-design.com/

Rememebr you will have to load each image and all one by one as the theme loader will only work for phbb themes especially designed for edit boards.