These characters have variously been described as Imperial "council members", Imperial "courtiers", and Imperial "advisors", as outlined below.
1) Most reliably, they are the Imperial "council members" that appear in scene 57 of the third (and final?) draft of the script, as presented here:
Darth Vader, standing with other members of the Imperial council, cautiously approaches his master. … Vader bows, then turns and exits the throne room as the Emperor walks toward the waiting council members.
2) Secondly, they are likely also the Imperial "courtiers" that appear on page 90 of the official 1983 novelization of the film, written by James Kahn and based on the screenplay by Lawrence Kasdan and George Lucas (as reproduced here on Google Books;
The main corridor was filled with courtiers, all awaiting an audience with the Emperor. Vader curled his lip at them—fools, all. Pompous toadys [sic] in their velvet robes and painted faces; perfumed bishops passing notes and passing judgements among themselves—for else who cared; oily favor-merchants, bent low from the weight of jewelry still warm from a previous owner's dying flesh; easy, violent men and women, lusting to be tampered with.
3) And finally, the Star Wars Wiki has a page for them under Imperial "advisors" here (which lists many references but few inline citations).
The Imperial advisors were a group of several hundred high ranking political bureaucrats of the Galactic Empire.
Here's a screenshot (from the original 1983 release of the film) of them exiting the Emperor's shuttle (barely visible behind his right shoulder) after landing in the Death Star:
Here's a wide shot of them walking behind the Emperor and Lord Vader, from that same scene:
Here's a second, better-lit angle of the pair in the Emperor's throne room:
Here's an uncredited photo of the whole group from the film set: