One of the challenges in creating Vault of the Galaxy is designing a universe filled with alien civilizations. Many of the tropes that work in Human Space—crime syndicates, space navies, etc.—aren't appropriate for alien races.
In this design request I'd like to hear about your favorite alien races (and alien civilizations) in fiction (books/movies/games) and how they might inspire us for Vault of the Galaxy.
To get things started, here are a few of my inspirations for some of the current alien races.
Larry Niven's Tales of Know Space
Though Ringworld is the more famous book, The Ringworld Engineers is probably my favorite. One of his races, called Pierson's puppeteers, is wonderfully incongruous, combining extreme cowardice with masterful long-term planning.
This book also introduced me to biogenetic transformation, as when the character Teela Brown eats a plant that mutates her into a Pak Protector: a creature with superhuman intelligence and strength biologically compelled to protect the Ringworld.
David Brin's Uplift Saga
This series has been hugely influential in science fiction. I believe it is the first book to use the word "uplift." It also popularized the now common trope (used in Star Control) of a long-dead and mysterious "progenitor" race from which all alien species emerged.
For Vault of the Galaxy I lifted his concept of "orders of sapient life" to design the various races in the galaxy. In Brin's universe, the galaxy is separated between oxygen-breathing and hydrogen-breathing races, though there are also other orders, such as transcendent, mechanical, memetic, and quantum.
Alastair Reynolds's Revelation Space Universe
Though I haven't read all the books in this series, my favorite part is the Lovecraftian setting, in which humans are but pawns to alien civilizations pursuing their own inscrutable agendas.
I read these books around 2010 or so, long after the core of the Transcendence universe was set, but we might be able to get some ideas for Part II.
What are some of your inspirations? Let me know in the comments.