There is no template file specifically for the random photo, we simply build a block and fill it.
but if you may, the block function is in plugins/G2Bridge/functions.inc
Geeklog does not allow for php in the footer, but you could create a staticpage, enable php execution, and set the contents to:
Text Formatted Code
and make this a centerblock at the bottom of the page
FlashYourWeb and Your Gallery with the E2 XML Media Player for Gallery2 - http://www.flashyourweb.com