This is one of the best ideas I've come across for a long time. It's the brainchild of Hilary and Josh, who celebrated their own wedding in October in California. They made their vows under a huge oak tree, and to continue the theme, decided to create a finger print tree as a commemorative guest book. The idea was such a huge hit, that they now sell peronalised empty trees on their Etsy shop, so you can buy them for your big day. Check out their inspirational wedding photos on the fab wedding blog Green Wedding Shoes.