At the moment I am focussing mainly on establishing the Kukru's appearance before I work on other characters, as they are the ones that require the most research and experimentation in terms of their physiology.
The idea for this race was the result of this sketch I did a while back:
All I knew when I drew this was that I wanted to draw something that wasn't a person, as I feel like that's often all I can draw. I did no research and didn't use references, so there's lots of room for improvement, but I liked the overall impression I got from the sketch - I began to envision ideas of what their towns and villages would be like, about their culture (for some reason drinking teas from a bowl was something I wanted to incorporate), and about their voices and hairstyles. So, I decided to use all this as part of the basis for one of the races in this project, though none of these ideas were set in stone and I knew I wanted to develop them a lot more.
The sketches below are further experiments. Like the concept drawings I posted below from the Mass Effect art book, I mainly wanted to sketch out a range of shapes and looks and to play with different features. I was leaning towards the idea of them being reptilian and/or bird-like, so I experimented drawing with and without beaks and varying degrees of human-like skull shapes.
(Sorry they're so messy... Being a lefty means that working on pages of drawings like this tends to cause them to smudge all over the place)