Without really knowing what you're looking for I don't know what to tell you (do you want goofy, serious, gracious, etc)?. Check out this link though, it may give you some help!
Slideshow Song Suggestions - Weddings, Anniversary, Graduations, Birthday Slideshow Songs. Sands of Time...
You can also try & google slide show music & you should be able to get some good suggestions. The end produvt will be awesome, but I do know that it can take a lot of time & thought to get there. Good luck & have fun with it!