Holmes Basic set and rulebook (page #s refer to 1st edition)
David C. Sutherland III - cover, title page (as SUTHERLAND III) and numerous interior illustrations
David Trampier - two interiors: web spell (pg 16, as DA TRAMPIER); warrior vs minotaur (pg 18)
Tom Wham - two interiors: sword (pg 35)*; gnolls/wizard (pg 26), as "TW"
Unknown - gray ooze on page 27 (1st edition only); possibly DCSIII
Unknown - Sample Cross Section of Levels (page 38), map of Sample Floor Plan (page 41); possibly DCSIII following designs by Holmes
*Thanks to Rhuvein on Dragonsfoot; he heard directly from Tom that he drew this sword.
Holmes Basic set and rulebook - UK version
John Blanche - front cover
Fangorn (aka Chris Baker) - interiors, many are re-drawings of the originals
Monster & Treasure Assortment - Set I
David C. Sutherland III - cover and interior illustrations
B1 In Search of the Unknown (monochrome)
David C. Sutherland III - cover (as DIS), back cover, all interiors (as DCS or SUTHERLAND III)
David Trampier - cover (as DAT)
The cover is credited to both artists. See here for Trampier's original version.
B2 Keep on the Borderlands (1st print - Wizard Logo; front cover mentions AD&D)
Jim Roslof - front cover, owlbear on title page (as ROSLOF) - (see here for a partial list of Roslof TSR illustrations)
Erol Otus (EO) - back cover, four interior illustrations (as EO)
David S. Laforce - two thematically linked interior illustrations on page 7 (as DSL)
B2 Keep on the Borderlands (2nd print - Wizard Logo; front cover does not mention AD&D)
Two pictures were added to this print in place of the section on using the module with AD&D
Unknown artist - intertwining snakes (page 5)
David C. Sutherland III - dragon (page 6). This Dragon illustration was originally used in last issue of Strategic Review (#7, April 1976, page 11) to advertise the upcoming debut of Dragon magazine (thanks to paleologos on Dragonsfoot for this info). It was then used in the 2nd print B2, along with the snakes illustration, to fill in deleted text referring to AD&D. It was not included in the revised Moldvay version of B2, but was instead used in the Moldvay version of B1.
Chapel of Silence in Dragon # 50
Roger Raupp - module cover illustration
The Creature of Rhyl in Dragon #55
Harry Quinn - module cover illustration and five interior illustrations
Boinger & Zereth stories by Dr. Holmes
Were-shark (Alarums & Excursions #13, July 1976) - one illo by Chris Holmes
The Adventure of the Giant Chameleon (Alarums & Excursions # 14, Aug 1976) - two illos by Chris Holmes
Trollshead (THE DRAGON #31, Nov 1979) - illustration by Chris Holmes
The Sorcerer's Jewel (DRAGON #46, Feb 1981) - illustrations by Jim Roslof
In the Bag (DRAGON #58, Feb 1982) - illustrations by Donna Barr
THE MAZE OF PERIL (1986) - cover Dan Day, frontispiece Gregorio Montejo.
Other articles in Dragon magazine by Dr. Holmes
Lovecraftian Mythos in D&D (THE DRAGON #12, Feb 78) - "From the Sorceror's Scroll" illustration, artist unknown
Lost Civilizations: Fantasy Supplement for Source of the Nile (THE DRAGON #12, Apr 1979) - title illustration by Chris Holmes