Having the issues right here in front of me I can say that it does indeed represent all of the company employees in 1976. They were all depicted as characteres in the soap-opera strip called "David Megarry, David Megarry" after "Mary Hartman, Mary Hartman".
From left to right we have Mike Carr (note the flying cap and WWI planes), Tim Kask (pipe and cap), Brian Blume (six-shooters and "50 Gallon Hat"), Ernie "The Barbarian" Gygax (carrying desk), Gary Gygax "The Commander in Grief" (riding desk), Terry Kuntz (carrying desk; dressed as Robin Hood), Dave Arneson (wearing "Blackmoor U" shirt), Rob Kuntz (towing a beholder by an eyestalk), and Neil Topolnicki (in Napoleonics regailia). In the building are Dave Sutherland and David Megarry (two voices simultaneous). According to my research that's every employee of the company circa May of 1976. Dave has other drawings, "Shlump Da Orc" for himself and David Megarry is depicted as an intoxicated halfling with loads of curly hair.
Futures Bright,
Paul