Heather Douglas (Moondragon)
In Guardians of the Galaxy, Drax the Destroyer (Dave Bautista) only lives for one purpose - to seek revenge against the character responsible for the death of his daughter and wife. Wouldn't it be interesting if in the films he learns that - just like in the comics - his daughter isn't actually dead?
Moondragon, who sports a bald head like Nebula (Karen Gillan), is a powerful telepath and martial artist with an epic story arc we won't spoil here. She's shared romantic relationships with other characters on this list including Phyla-Vell, the original Quasar and even Thor, and has an important role to play in the 2008-2010 Guardians of the Galaxy comics.
Phyla-Vell (Quasar, Captain Marvel, Martyr)
A relatively new character in Marvel Comics, Phyla is the daughter of Mar-Vell (the original Captain Marvel) who takes on the mantle and powers of Quasar after Wendell Vaughn dies protecting the galaxy. A love interest of Moondragon and a close friend of Drax, Phyla later joins the Guardians of the Galaxy and takes on an important role in the major space-based events by Dan Abnett and Andy Lanning.
We met the Kree in Guardians of the Galaxy so we'll definitely see more Kree characters in followups.
Vance Astro (Major Victory)
After the Annihilation and Annihilation: Conquest space crossover events by Dan Abnett and Andy Lanning helped setup the formation of the Guardians of the Galaxy, Peter Quill and his team's first mission saw them encounter a man frozen in time and space with the shield of Captain America. The character was Vance Astro from the future, a founding member of the original Guardians of the Galaxy team from the 1968 Marvel Comics team.
He becomes a full member of the team and in future GOTG movies would offer another throwback to the original roster much like Yondu (Michael Rooker) was in James Gunn's first movie. If the movies explore time-travel, and they will eventually with the introduction of the Time Infinity Stone, Astro would be a key character to play with - especially if he has Cap's shield from the future.
Another Kree character on our list, Noh-Varr is the sole survivor of a Kree starship who declares war on Earth and Humanity. After some run-ins with S.H.I.E.L.D. and key Earth superheroes he vows to become a defender of our planet, becoming the new Captain Marvel. He's later given a new suit by the Kree and takes on the name Protector.
Noh-Varr has served with The Avengers, and Iron Man takes particular interest in Noh-Varr because of his knowledge and technologies. While never a member of the Guardians of the Galaxy in the comics, we'd love to see a Noh-Varr subplot bridging the gap between Earth and the Kree homeworld, and story that could also potentially include Carol Danvers (Ms. Marvel) - a half-human/half-kree character often rumored to be potentially introduced in The Avengers: Age of Ultron.