Pictures of old prospectors would be good.You could also have pictures of old hound dogs,like bloodhounds.You could also make prop cakes with an exaggerated amount of candles.
Make the banner green and wavy, like hills. Top each letter with flowers to make it look like they're "growing"; if he's a geek, replicate Bilbo Baggins's hobbit hole!
Decorate tabletops with vases of dead flowers with dentures placed in the water. Photoshop his photos, adding comical "old man" details, for a birthday display or to use as placemats.
