I’ve seen this done here and there at weddings featured on several wedding blogs and I think it is a really creative alternative to a guest book. Guests use ink to place their fingerprints on a tree and sign their names. I thought it may be more appropriate for a green-ish (color and/or themed) wedding, but I came across this example with colors similar to those I’d like to incorporate into my wedding featured at this wedding on SMP:
The Budget-Minded Bride Blog also posted this example:
Although green tones aren’t out of the question! This beautiful example featured on A Wedding Diary:
Bleudetoi on Etsy has a wide selection of fingerprint trees! Definitely something to consider...