The Battle of Carkoon was one of the showpieces of Return of the Jedi and included a number of interesting looking creatures to battle the heroes over the pit containing the deadly Sarlacc. The groups can be broken down into three locations; those on skiff one, those on skiff two and those on the sail barge. While Jabba's palace featured a vast range of alien types, the Battle of Carkoon primarily featured three types of aliens as well as humans.
Skiff one contains the prisoners, Luke Skywalker, Chewbacca, Han Solo, a diguised Lando Calrissian, and the guards.
Vedain: A Red Nikto from the planet Kintan, Vedain is the pilot of the skiff and the guard knocked over the side with Lando Calrissian.
Unidentified Weequay : There are a number of Weequay guards featured in the battle. The species hails from the planet Sriluur. This one is the skiff master.
Velken Tezeri: Human skiff guard. He was the first to fall into the sarlacc.
Kithaba: A Klatooinian from Klatooine. He'sd the first guard to be knocked off the skiff by Luke, but manages to evade the sarlacc's tentacles until near the end of the battle.
Weequay skiff guard
Skiff two. Front to back: Sgt. Doallyn, Nikto guard, Pote Snitkin, Gailid, Barada, unknown mercenary pilot, Yotts Oren.
Sergeant Doallyn: A hydron-three breathing Geran from the planet Geran. He is first seen being thrown down the stairs by Chewbacca when the wookiee is led in as a "prisoner" of the disguised Leia.
Unnamed Red Nikto skiff guard.
Pote Snitkin: A Skrilling from Agworld - 2079. Pilot of skiff two.
Gailid: Human. Killed by Luke Skywalker.
Barada: Klatooinian from Klatooine.
Unknown mercenary pilot.
Yotts Oren: Green Nikto from Kintan
Here are the bulk of the guards from Jabba's Sail Barge...
Unnamed human guard and Klaatu, a Green Nikto guard.
Unnamed human guard.
Taym Dren-garen: Human guard. He's the one who shoots Luke in the hand.
Unnamed Weequay guard.
Another unnamed Weequay guard.
Nysad: A Red Nikto guard.
Vizam: A Red Nikto guard.
Klaatu: A Green Nikto guard.
Wooof: A Green Nikto guard.
Below are production masks for some of the above characters. Before I get to them, I want to say that the above names are from the now official canon sprung out of the expanded universe when background extras needed to be given names for role playing games and action figures rather than simply being called "green alien hitman." These names grew out of what the crew called the various characters in costume for scheduling and continuity. They also now have extensive biographies, which are often ridiculous, and which I've chosen to ignore.
I understand the reasoning behind doing this, but often times it makes matters confusing, and is often illogical. Lucasfilm's own notes on the the four primary non-human skiff guards are provided below the photos of their masks.
Nikto: A humanoid species with flat faces and multiple nostrils.
Klaatu: A reptilian, a variant strain of the Nikto known as fierce fighters and having cold obsidian-black eyes.
Barada: A native of Klatooine.
Weequay: Inspired by the Queequeg character in Moby Dick, and was referred to as Queequay by the ILM crew.
These seem to have been meant as species names, which is doubly confusing because Klaatu is now the name of an individual instead of a type, or species, and also because in spite of what it says, the Nikto and Klaatu do not look at all like they are divergent from one another as related species from the same planet, so calling then Red Nikto and Green Nikto makes little sense. You will notice that in other entries regarding merchandise, I've gone back to using their more generic names. Klaatu is any alien of that species and so on.
Also, it should be pointed out for those of you who don't know, that Klaatu, Barada, and Nikto were the three word instructions for deactivating the robot, Gort in the science fiction classic, The Day the Earth Stood Still (1951).