My vote goes either to the Dhayut, the Securans or the Wekkarus.
The Securans, because they are one of races that are the closest to humans, so it would be appropriate to have a similar diversity among their characters.
The Dhayut, because I love spiders and I think you could have a great diversity of portraits. For example, portraits for agents could be inspired by jumping spider heads, portraits for warrior charaters could e inspired by wolf spiders, and so on.
The Wekkarus, simply because they are cool. By the way, I think their galactopedia entry should be changed. It says they are crusteans, but their new art displays them as squid-like creatures.