My vote is based 90% on concept and less so on technique (I think having more than a week would allow all the entrants to get to a more finished point). I also focused on "alien" first and "siren" second. I think going with a human figure wasn't the best concept choice for an alien, so while there are some great figures out there, I had to go with alien.
1. Mhugo - I think the type of wings you went with really indicate a lure, and I like the shape of the creature and its pose.
2. Paperdreams (even based on the most recent WIP before final) - the purpose of the siren is very clear without any description; I think a good concept should do this within seconds.
3. niobe - I like the design of the top of the head. The limbs, torso, and fingers also seem very alien, but luring and soft.
3.5. S Winterflood - This concept felt very alien and aggressive.