Since they had an appreciation for Shakespeare, a popular version of Macbeth was re-envisioned by the Arcturians. Sponsored by the Galactic Cultural Exchange Project, this rendition was notably performed by the Karidian Company of Players, a touring theatrical troupe headed by Anton Karidian, in 2266. (TOS: "The Conscience of the King")
An Arcturian Starfleet officer was speaking with two Vegans at Starfleet Headquarters air tram station in San Francisco on stardate 7410.2. The three were on a lower platform (in the background) when James T. Kirk and Sonak parted ways at the top of a flight of stairs.
The Arcturians were designed by Fred Phillips and Robert Fletcher for The Motion Picture. With the approval of Gene Roddenberry, the Arcturians, as well as numerous other new species in the film, were named by Fletcher and provided a backstory by him. The following is a brief description, in Fletcher's own words:
"ARCTURIANS – A militaristic race of great armies. All are identical – they clone each other, can only tell apart by color of uniforms. Provide infantry for Federation. Planet is enormous and population enormous, subject to any amount of expansion; 100 billion population, army of 20 billion ready overnight. Costume – contains leather and linen. Boots are separate. (Bob wanted woven metal tubes for metal rope decorations; found in obsolete plumbing equipment in an old hardware store; silver-plated it for bandolier [jewelry] and for decoration on shoulders and elbows, denoting rank and regiment.) Briefcase made of plastic, belt buckle of cast metal and resin." (The Making of Star Trek: The Motion Picture, p. 130)
"A massive militaristic society, the Arcturians are the race which provides the infantry for the Federation. Their home planet is enormous and likewise their population – over 100 billion strong at last count. Therefore, producing an army of 20 billion overnight is a snap for them. There is, however, one problem. Since all Arcturians are produced by cloning they all look alike. They have overcome this problem easily by using a color coded designation for regiment and rank. But woe to the poor Federation general who suffers from color blindness."  
In an interview appearing in the March 1980 edition of Fantastic Films, part two of "The Star Trek Costumes", Fletcher revealed more information about the Arcturians and the design of their costumes, explaining:
"Only one society was militaristic in our sense of the word. That was the Arcturians, the cloned people who all looked alike. The only way to tell them apart was the coloring of their uniforms. For them we created costumes of leather and linen and originally I wanted woven metal tubes for metal rope decorations. Bob found this material in an obsolete plumbing/hardware store. It was to be silver-plated into a bandolier and also used for decorations on the shoulders and elbows denoting rank and regiment. It didn't quite work out so you'll see very little of it in the film, toned down quite a bit. Also, we even created a small briefcase made of plastic, something like the pilots carry today."
A 1979 documentary, The Making of Star Trek: The Motion Picture, confirmed the militaristic intent for the Arcturians, where it was specifically mentioned that they provided the "infantry for the Federation." That notion was reaffirmed decades later, in an article appearing in the January 2002 edition of Star Trek: The Magazine Volume 2, Issue 9, entitled "Who is that Alien?", which stated:
"A race of clones from the densely populated Arcturas [sic]. Fred Phillips and Robert Fletcher speculated that they provided the backbone of the Federation infantry – not least because, if needed, they could clone billions of new soldiers overnight."
The costume for the Arcturian who is visible on the Enterprise's rec deck in The Motion Picture was prepared for filming by assistant makeup artist Mike La Valley. (The Making of Star Trek: The Motion Picture, interior color photographs)
Arcturians also occasionally appeared in the Star Trek newspaper comic strip.