These credits were not included in the rule book, since they were not known at the time. Listed is the page number, name of artist, and source document for each piece below. Courtesy of Spaghetti Spaceships (pahoota) via RPGGeek. Page 6, Earle Bergey, Startling Stories (July, 1950)
Page 10, Allen Anderson, Planet Stories (March, 1952)
Page 23, Malcolm Smith, Fantastic Adventures (December, 1938)
Page 32, Arnold Kohn, Amazing Stories (August, 1947)
Page 39, George Rozen, Planet Stories (May, 1943)
Page 66, Howard V. Brown, Thrilling Wonder Stories (December, 1938)
Page 68, Malcolm Smith, Operation Interstellar (Novel), 1950)
Page 79, C.L. Hartman, Amazing Stories (February, 1940)
Page 100, Allen Anderson, Planet Stories (Spring, 1950)
Page 103, L. Sterne Stevens, Amazing Stories (May, 1952)
Page 107, Gloria Stoll, Dime Mystery Magazine (November , 1943)
Page 110, Richard Loehle, Amazing Stories (September, 1949)
Page 136, H. W. Scott, Western Stories (January, 1939)
Page 153, Hadden, Amazing Stories (June, 1943)
Page 166, Norman Saunders, Western Romances (v24, #71, April 1937)
Page 178, Earle Bergey, Startling Stories (July, 1949)
Page 193, Allen Anderson, Planet Stories (November, 1952)
Page 198, H. W. McCauley, Amazing Stories (March, 1940)
Page 201, Walter Baumhofer, Dime Western Magazine (v8 #2, January 1, 1935)
Page 202, Earle Bergey, Thrilling Wonder Stories (December, 1950)
Page 203, Howard V. Brown, Thrilling Wonder Stories (June, 1940)
Page 205 (Left), E.K. Bergey, Startling Stories (September, 1940 )
Page 205 (Right), Walter Baumhofer, Speakeasy Stories (June-July, 1931)
Page 206, Edmond Swiatek, Amazing Stories (March, 1949)
Page 208, Earle Bergey, Thrilling Wonder Stories (October, 1950)
Page 209, Unknown, .44 Western (April, 1941)
Page 215, J. Allen St. John, Amazing Stories (August, 1941)
Page 218, Robert Fuqua, Fantastic Adventures (February, 1940)