You can get more info about the book itself here: http://www.amazon.com/Aquarius-Rising-ebook/dp/B00CFP88H0
The creatures are mermaid-like humanoids...
Here's a bit of the description of the creatures from an expert from the book:
"Revelers floated everywhere. Strings of limpets, whelks, and periwinkles glittered around their necks, clicking when they moved. Brightly colored pigments stained their skin of blue and gray and silver with pictograms symbolizing the history of Aquarius.
Auriga floated a few meters away, skin gleaming silver in the sunlight, the fin ridges along her arms and legs and ear channels paling to a milky white. She had smeared her body with stripes of ebony and gold to mimic the markings of the butterfly fish from which she took her name. The sight of her made him ache."
At this point I made a list of their traits, and just started doodling. Playing with various eye and body shapes and a few pose examples.
I emailed this in and got some feed back about the design, and then jumped to the next phase.
The actual drawing of the Aquarians:
Everyone was pleased with the drawings, so I scanned them in for final coloring!
...and this is how it all turned out:
