In 10.4, when you start a slide show from Finder (highlight the photos you want and control-click, then pick Slideshow), you can move the control bar that shows up at the bottom of the screen.
All you have to do is click on it somewhere other than the buttons and drag it to where you want it. For better or for worse, the position resets the next time.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050506115810962