Thanks for linking to the site, I enjoyed going through them to find my own selection. I liked the second place winner the most from NatGeo's own finalists, the baobab trees in your favourite image are neat.
Based on the same format here are my choices for the awards, the merit prizes being in no order and with one additional listed to replace the Viewers' Choice Winner for obvious reasons. The images are hyperlinked to the relevant NatGeo page including description and enlarged images.