First Half of the Alternate Character Interpretation prompt.

From left to right:

Hosanna Cutting-Green: previously seen in the Personal Space picture, usually the daughter of a deeply sexist human culture. 

Kesamari Dabain:
previously seen in the character sheet pictures, as well as the currently defunct Staff. Usually female, from a species with a huge gender imbalance. 

Chren and Mehrn:
Not from an art challenge yet, but from the ongoing Skyfall comic. Members of a species with very few reproductively mature individuals.

More about all this on the blog, of course of course.